Wikipedia-listeartikel
Denne liste over matematiske serier indeholder formler for endelige og uendelige summer. Det kan bruges sammen med andre værktøjer til vurdering af beløb.
Her tages for at have værdien
0
0
{\ displaystyle 0 ^ {0}}
1
{\ displaystyle 1}
{
x
}
{\ displaystyle \ {x \}}
betegner den brøkdel af
x
{\ displaystyle x}
B
n
(
x
)
{\ displaystyle B_ {n} (x)}
er et Bernoulli-polynom .
B
n
{\ displaystyle B_ {n}}
er et Bernoulli-nummer , og her,
B
1
=
-
1
2
.
{\ displaystyle B_ {1} = - {\ frac {1} {2}}.}
E
n
{\ displaystyle E_ {n}}
er et Euler-nummer .
ζ
(
s
)
{\ displaystyle \ zeta (s)}
er Riemann zeta-funktionen .
Γ
(
z
)
{\ displaystyle \ Gamma (z)}
er gamma-funktionen .
ψ
n
(
z
)
{\ displaystyle \ psi _ {n} (z)}
er en polygammafunktion .
Li
s
(
z
)
{\ displaystyle \ operatorname {Li} _ {s} (z)}
er en polylogaritme .
(
n
k
)
{\ displaystyle n \ vælg k}
er binomial koefficient
eksp
(
x
)
{\ displaystyle \ exp (x)}
betegner eksponentiel af
x
{\ displaystyle x}
Summer af kræfter
Se Faulhabers formel .
∑
k
=
0
m
k
n
-
1
=
B
n
(
m
+
1
)
-
B
n
n
{\ displaystyle \ sum _ {k = 0} ^ {m} k ^ {n-1} = {\ frac {B_ {n} (m + 1) -B_ {n}} {n}}}
De første få værdier er:
∑
k
=
1
m
k
=
m
(
m
+
1
)
2
{\ displaystyle \ sum _ {k = 1} ^ {m} k = {\ frac {m (m + 1)} {2}}}
∑
k
=
1
m
k
2
=
m
(
m
+
1
)
(
2
m
+
1
)
6
=
m
3
3
+
m
2
2
+
m
6
{\ displaystyle \ sum _ {k = 1} ^ {m} k ^ {2} = {\ frac {m (m + 1) (2m + 1)} {6}} = {\ frac {m ^ {3 }} {3}} + {\ frac {m ^ {2}} {2}} + {\ frac {m} {6}}}
∑
k
=
1
m
k
3
=
[
m
(
m
+
1
)
2
]
2
=
m
4
4
+
m
3
2
+
m
2
4
{\ displaystyle \ sum _ {k = 1} ^ {m} k ^ {3} = \ left [{\ frac {m (m + 1)} {2}} \ right] ^ {2} = {\ frac {m ^ {4}} {4}} + {\ frac {m ^ {3}} {2}} + {\ frac {m ^ {2}} {4}}}
Se zeta-konstanter .
ζ
(
2
n
)
=
∑
k
=
1
∞
1
k
2
n
=
(
-
1
)
n
+
1
B
2
n
(
2
π
)
2
n
2
(
2
n
)
!
{\ displaystyle \ zeta (2n) = \ sum _ {k = 1} ^ {\ infty} {\ frac {1} {k ^ {2n}}} = (- 1) ^ {n + 1} {\ frac {B_ {2n} (2 \ pi) ^ {2n}} {2 (2n)!}}}
De første få værdier er:
ζ
(
2
)
=
∑
k
=
1
∞
1
k
2
=
π
2
6
{\ displaystyle \ zeta (2) = \ sum _ {k = 1} ^ {\ infty} {\ frac {1} {k ^ {2}}} = {\ frac {\ pi ^ {2}} {6 }}}
( Basel-problemet )
ζ
(
4
)
=
∑
k
=
1
∞
1
k
4
=
π
4
90
{\ displaystyle \ zeta (4) = \ sum _ {k = 1} ^ {\ infty} {\ frac {1} {k ^ {4}}} = {\ frac {\ pi ^ {4}} {90 }}}
ζ
(
6
)
=
∑
k
=
1
∞
1
k
6
=
π
6
945
{\ displaystyle \ zeta (6) = \ sum _ {k = 1} ^ {\ infty} {\ frac {1} {k ^ {6}}} = {\ frac {\ pi ^ {6}} {945 }}}
Power-serien
Polylogaritmer med lav ordre
Endelige summer:
∑
k
=
m
n
z
k
=
z
m
-
z
n
+
1
1
-
z
{\ displaystyle \ sum _ {k = m} ^ {n} z ^ {k} = {\ frac {z ^ {m} -z ^ {n + 1}} {1-z}}}
, ( geometrisk serie )
∑
k
=
0
n
z
k
=
1
-
z
n
+
1
1
-
z
{\ displaystyle \ sum _ {k = 0} ^ {n} z ^ {k} = {\ frac {1-z ^ {n + 1}} {1-z}}}
∑
k
=
1
n
z
k
=
1
-
z
n
+
1
1
-
z
-
1
=
z
-
z
n
+
1
1
-
z
{\ displaystyle \ sum _ {k = 1} ^ {n} z ^ {k} = {\ frac {1-z ^ {n + 1}} {1-z}} - 1 = {\ frac {zz ^ {n + 1}} {1-z}}}
∑
k
=
1
n
k
z
k
=
z
1
-
(
n
+
1
)
z
n
+
n
z
n
+
1
(
1
-
z
)
2
{\ displaystyle \ sum _ {k = 1} ^ {n} kz ^ {k} = z {\ frac {1- (n + 1) z ^ {n} + nz ^ {n + 1}} {(1 -z) ^ {2}}}}
∑
k
=
1
n
k
2
z
k
=
z
1
+
z
-
(
n
+
1
)
2
z
n
+
(
2
n
2
+
2
n
-
1
)
z
n
+
1
-
n
2
z
n
+
2
(
1
-
z
)
3
{\ displaystyle \ sum _ {k = 1} ^ {n} k ^ {2} z ^ {k} = z {\ frac {1 + z- (n + 1) ^ {2} z ^ {n} + (2n ^ {2} + 2n-1) z ^ {n + 1} -n ^ {2} z ^ {n + 2}} {(1-z) ^ {3}}}}
∑
k
=
1
n
k
m
z
k
=
(
z
d
d
z
)
m
1
-
z
n
+
1
1
-
z
{\ displaystyle \ sum _ {k = 1} ^ {n} k ^ {m} z ^ {k} = \ left (z {\ frac {d} {dz}} \ right) ^ {m} {\ frac {1-z ^ {n + 1}} {1-z}}}
Uendelige summer, gyldige for (se polylogaritme ):
|
z
|
<
1
{\ displaystyle | z | <1}
Li
n
(
z
)
=
∑
k
=
1
∞
z
k
k
n
{\ displaystyle \ operatorname {Li} _ {n} (z) = \ sum _ {k = 1} ^ {\ infty} {\ frac {z ^ {k}} {k ^ {n}}}}
Følgende er en nyttig egenskab til at beregne polylogaritmer med lavt helt orden rekursivt i lukket form :
d
d
z
Li
n
(
z
)
=
Li
n
-
1
(
z
)
z
{\ displaystyle {\ frac {\ mathrm {d}} {\ mathrm {d} z}} \ operatorname {Li} _ {n} (z) = {\ frac {\ operatorname {Li} _ {n-1} (z)} {z}}}
Li
1
(
z
)
=
∑
k
=
1
∞
z
k
k
=
-
ln
(
1
-
z
)
{\ displaystyle \ operatorname {Li} _ {1} (z) = \ sum _ {k = 1} ^ {\ infty} {\ frac {z ^ {k}} {k}} = - \ ln (1- z)}
Li
0
(
z
)
=
∑
k
=
1
∞
z
k
=
z
1
-
z
{\ displaystyle \ operatorname {Li} _ {0} (z) = \ sum _ {k = 1} ^ {\ infty} z ^ {k} = {\ frac {z} {1-z}}}
Li
-
1
(
z
)
=
∑
k
=
1
∞
k
z
k
=
z
(
1
-
z
)
2
{\ displaystyle \ operatorname {Li} _ {- 1} (z) = \ sum _ {k = 1} ^ {\ infty} kz ^ {k} = {\ frac {z} {(1-z) ^ { 2}}}}
Li
-
2
(
z
)
=
∑
k
=
1
∞
k
2
z
k
=
z
(
1
+
z
)
(
1
-
z
)
3
{\ displaystyle \ operatorname {Li} _ {- 2} (z) = \ sum _ {k = 1} ^ {\ infty} k ^ {2} z ^ {k} = {\ frac {z (1 + z )} {(1-z) ^ {3}}}}
Li
-
3
(
z
)
=
∑
k
=
1
∞
k
3
z
k
=
z
(
1
+
4
z
+
z
2
)
(
1
-
z
)
4
{\ displaystyle \ operatorname {Li} _ {- 3} (z) = \ sum _ {k = 1} ^ {\ infty} k ^ {3} z ^ {k} = {\ frac {z (1 + 4z + z ^ {2})} {(1-z) ^ {4}}}}
Li
-
4
(
z
)
=
∑
k
=
1
∞
k
4
z
k
=
z
(
1
+
z
)
(
1
+
10
z
+
z
2
)
(
1
-
z
)
5
{\ displaystyle \ operatorname {Li} _ {- 4} (z) = \ sum _ {k = 1} ^ {\ infty} k ^ {4} z ^ {k} = {\ frac {z (1 + z ) (1 + 10z + z ^ {2})} {(1-z) ^ {5}}}}
Eksponentiel funktion
∑
k
=
0
∞
z
k
k
!
=
e
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {z ^ {k}} {k!}} = e ^ {z}}
∑
k
=
0
∞
k
z
k
k
!
=
z
e
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} k {\ frac {z ^ {k}} {k!}} = ze ^ {z}}
(jf. gennemsnit af Poisson-fordeling )
∑
k
=
0
∞
k
2
z
k
k
!
=
(
z
+
z
2
)
e
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} k ^ {2} {\ frac {z ^ {k}} {k!}} = (z + z ^ {2}) e ^ {z }}
(jf. andet øjeblik af Poisson-distribution)
∑
k
=
0
∞
k
3
z
k
k
!
=
(
z
+
3
z
2
+
z
3
)
e
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} k ^ {3} {\ frac {z ^ {k}} {k!}} = (z + 3z ^ {2} + z ^ {3 }) e ^ {z}}
∑
k
=
0
∞
k
4
z
k
k
!
=
(
z
+
7
z
2
+
6
z
3
+
z
4
)
e
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} k ^ {4} {\ frac {z ^ {k}} {k!}} = (z + 7z ^ {2} + 6z ^ {3 } + z ^ {4}) e ^ {z}}
∑
k
=
0
∞
k
n
z
k
k
!
=
z
d
d
z
∑
k
=
0
∞
k
n
-
1
z
k
k
!
=
e
z
T
n
(
z
)
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} k ^ {n} {\ frac {z ^ {k}} {k!}} = z {\ frac {d} {dz}} \ sum _ {k = 0} ^ {\ infty} k ^ {n-1} {\ frac {z ^ {k}} {k!}} \, \! = e ^ {z} T_ {n} (z) }
hvor er Touchard polynomierne .
T
n
(
z
)
{\ displaystyle T_ {n} (z)}
Trigonometrisk, invers trigonometrisk, hyperbolsk og invers hyperbolsk funktionsforhold
∑
k
=
0
∞
(
-
1
)
k
z
2
k
+
1
(
2
k
+
1
)
!
=
synd
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k} z ^ {2k + 1}} {(2k + 1)!}} = \ sin z}
∑
k
=
0
∞
z
2
k
+
1
(
2
k
+
1
)
!
=
sinh
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {z ^ {2k + 1}} {(2k + 1)!}} = \ sinh z}
∑
k
=
0
∞
(
-
1
)
k
z
2
k
(
2
k
)
!
=
cos
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k} z ^ {2k}} {(2k)!}} = \ cos z}
∑
k
=
0
∞
z
2
k
(
2
k
)
!
=
koselig
z
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {z ^ {2k}} {(2k)!}} = \ cosh z}
∑
k
=
1
∞
(
-
1
)
k
-
1
(
2
2
k
-
1
)
2
2
k
B
2
k
z
2
k
-
1
(
2
k
)
!
=
tan
z
,
|
z
|
<
π
2
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1} (2 ^ {2k} -1) 2 ^ {2k} B_ {2k} z ^ {2k-1}} {(2k)!}} = \ Tan z, | z | <{\ frac {\ pi} {2}}}
∑
k
=
1
∞
(
2
2
k
-
1
)
2
2
k
B
2
k
z
2
k
-
1
(
2
k
)
!
=
tanh
z
,
|
z
|
<
π
2
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(2 ^ {2k} -1) 2 ^ {2k} B_ {2k} z ^ {2k-1}} {(2k) !}} = \ tanh z, | z | <{\ frac {\ pi} {2}}}
∑
k
=
0
∞
(
-
1
)
k
2
2
k
B
2
k
z
2
k
-
1
(
2
k
)
!
=
barneseng
z
,
|
z
|
<
π
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k} 2 ^ {2k} B_ {2k} z ^ {2k-1}} {(2k)! }} = \ cot z, | z | <\ pi}
∑
k
=
0
∞
2
2
k
B
2
k
z
2
k
-
1
(
2
k
)
!
=
coth
z
,
|
z
|
<
π
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {2 ^ {2k} B_ {2k} z ^ {2k-1}} {(2k)!}} = \ coth z, | z | <\ pi}
∑
k
=
0
∞
(
-
1
)
k
-
1
(
2
2
k
-
2
)
B
2
k
z
2
k
-
1
(
2
k
)
!
=
csc
z
,
|
z
|
<
π
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k-1} (2 ^ {2k} -2) B_ {2k} z ^ {2k-1} } {(2k)!}} = \ Csc z, | z | <\ pi}
∑
k
=
0
∞
-
(
2
2
k
-
2
)
B
2
k
z
2
k
-
1
(
2
k
)
!
=
csch
z
,
|
z
|
<
π
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {- (2 ^ {2k} -2) B_ {2k} z ^ {2k-1}} {(2k)!}} = \ operatorname {csch} z, | z | <\ pi}
∑
k
=
0
∞
(
-
1
)
k
E
2
k
z
2
k
(
2
k
)
!
=
sech
z
,
|
z
|
<
π
2
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k} E_ {2k} z ^ {2k}} {(2k)!}} = \ operatorname {sech } z, | z | <{\ frac {\ pi} {2}}}
∑
k
=
0
∞
E
2
k
z
2
k
(
2
k
)
!
=
sek
z
,
|
z
|
<
π
2
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {E_ {2k} z ^ {2k}} {(2k)!}} = \ sec z, | z | <{\ frac { \ pi} {2}}}
∑
k
=
1
∞
(
-
1
)
k
-
1
z
2
k
(
2
k
)
!
=
ver
z
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1} z ^ {2k}} {(2k)!}} = \ operatorname {ver} z }
( versine )
∑
k
=
1
∞
(
-
1
)
k
-
1
z
2
k
2
(
2
k
)
!
=
hav
z
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1} z ^ {2k}} {2 (2k)!}} = \ operatorname {hav} z}
( haversine )
∑
k
=
0
∞
(
2
k
)
!
z
2
k
+
1
2
2
k
(
k
!
)
2
(
2
k
+
1
)
=
bueskind
z
,
|
z
|
≤
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(2k)! z ^ {2k + 1}} {2 ^ {2k} (k!) ^ {2} (2k + 1 )}} = \ arcsin z, | z | \ leq 1}
∑
k
=
0
∞
(
-
1
)
k
(
2
k
)
!
z
2
k
+
1
2
2
k
(
k
!
)
2
(
2
k
+
1
)
=
arsinh
z
,
|
z
|
≤
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k} (2k)! z ^ {2k + 1}} {2 ^ {2k} (k!) ^ {2} (2k + 1)}} = \ operatornavn {arsinh} {z}, | z | \ leq 1}
∑
k
=
0
∞
(
-
1
)
k
z
2
k
+
1
2
k
+
1
=
arctan
z
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(-1) ^ {k} z ^ {2k + 1}} {2k + 1}} = \ arctan z, | z | <1}
∑
k
=
0
∞
z
2
k
+
1
2
k
+
1
=
artanh
z
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {z ^ {2k + 1}} {2k + 1}} = \ operatorname {artanh} z, | z | <1}
ln
2
+
∑
k
=
1
∞
(
-
1
)
k
-
1
(
2
k
)
!
z
2
k
2
2
k
+
1
k
(
k
!
)
2
=
ln
(
1
+
1
+
z
2
)
,
|
z
|
≤
1
{\ displaystyle \ ln 2+ \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1} (2k)! z ^ {2k}} {2 ^ {2k + 1} k (k!) ^ {2}}} = \ ln \ left (1 + {\ sqrt {1 + z ^ {2}}} \ right), | z | \ leq 1}
Modificerede faktor nævnere
∑
k
=
0
∞
(
4
k
)
!
2
4
k
2
(
2
k
)
!
(
2
k
+
1
)
!
z
k
=
1
-
1
-
z
z
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {(4k)!} {2 ^ {4k} {\ sqrt {2}} (2k)! (2k + 1)!}} z ^ {k} = {\ sqrt {\ frac {1 - {\ sqrt {1-z}}} {z}}}, | z | <1}
∑
k
=
0
∞
2
2
k
(
k
!
)
2
(
k
+
1
)
(
2
k
+
1
)
!
z
2
k
+
2
=
(
bueskind
z
)
2
,
|
z
|
≤
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {2 ^ {2k} (k!) ^ {2}} {(k + 1) (2k + 1)!}} z ^ {2k + 2} = \ left (\ arcsin {z} \ right) ^ {2}, | z | \ leq 1}
∑
n
=
0
∞
∏
k
=
0
n
-
1
(
4
k
2
+
a
2
)
(
2
n
)
!
z
2
n
+
∑
n
=
0
∞
a
∏
k
=
0
n
-
1
[
(
2
k
+
1
)
2
+
a
2
]
(
2
n
+
1
)
!
z
2
n
+
1
=
e
a
bueskind
z
,
|
z
|
≤
1
{\ displaystyle \ sum _ {n = 0} ^ {\ infty} {\ frac {\ prod _ {k = 0} ^ {n-1} (4k ^ {2} + \ alpha ^ {2})} { (2n)!}} Z ^ {2n} + \ sum _ {n = 0} ^ {\ infty} {\ frac {\ alpha \ prod _ {k = 0} ^ {n-1} [(2k + 1 ) ^ {2} + \ alpha ^ {2}]} {(2n + 1)!}} Z ^ {2n + 1} = e ^ {\ alpha \ arcsin {z}}, | z | \ leq 1}
Binomiale koefficienter
(
1
+
z
)
a
=
∑
k
=
0
∞
(
a
k
)
z
k
,
|
z
|
<
1
{\ displaystyle (1 + z) ^ {\ alpha} = \ sum _ {k = 0} ^ {\ infty} {\ alpha \ vælg k} z ^ {k}, | z | <1}
(se Binomial sætning § Newtons generelle binomiale sætning )
∑
k
=
0
∞
(
a
+
k
-
1
k
)
z
k
=
1
(
1
-
z
)
a
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {{\ alpha + k-1} \ vælg k} z ^ {k} = {\ frac {1} {(1-z) ^ {\ alfa}}}, | z | <1}
∑
k
=
0
∞
1
k
+
1
(
2
k
k
)
z
k
=
1
-
1
-
4
z
2
z
,
|
z
|
≤
1
4
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {1} {k + 1}} {2k \ vælg k} z ^ {k} = {\ frac {1 - {\ sqrt { 1-4z}}} {2z}}, | z | \ leq {\ frac {1} {4}}}
, der genererer funktion af de catalanske tal
∑
k
=
0
∞
(
2
k
k
)
z
k
=
1
1
-
4
z
,
|
z
|
<
1
4
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {2k \ vælg k} z ^ {k} = {\ frac {1} {\ sqrt {1-4z}}}, | z | <{ \ frac {1} {4}}}
, der genererer funktion af de centrale binomiale koefficienter
∑
k
=
0
∞
(
2
k
+
a
k
)
z
k
=
1
1
-
4
z
(
1
-
1
-
4
z
2
z
)
a
,
|
z
|
<
1
4
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {2k + \ alpha \ vælg k} z ^ {k} = {\ frac {1} {\ sqrt {1-4z}}} \ venstre ({ \ frac {1 - {\ sqrt {1-4z}}} {2z}} \ højre) ^ {\ alpha}, | z | <{\ frac {1} {4}}}
Harmoniske numre
(Se harmoniske tal , selv defineret )
H
n
=
∑
j
=
1
n
1
j
{\ textstyle H_ {n} = \ sum _ {j = 1} ^ {n} {\ frac {1} {j}}}
∑
k
=
1
∞
H
k
z
k
=
-
ln
(
1
-
z
)
1
-
z
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} H_ {k} z ^ {k} = {\ frac {- \ ln (1-z)} {1-z}}, | z | < 1}
∑
k
=
1
∞
H
k
k
+
1
z
k
+
1
=
1
2
[
ln
(
1
-
z
)
]
2
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {H_ {k}} {k + 1}} z ^ {k + 1} = {\ frac {1} {2}} \ venstre [\ ln (1-z) \ højre] ^ {2}, \ qquad | z | <1}
∑
k
=
1
∞
(
-
1
)
k
-
1
H
2
k
2
k
+
1
z
2
k
+
1
=
1
2
arctan
z
log
(
1
+
z
2
)
,
|
z
|
<
1
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1} H_ {2k}} {2k + 1}} z ^ {2k + 1} = { \ frac {1} {2}} \ arctan {z} \ log {(1 + z ^ {2})}, \ qquad | z | <1}
∑
n
=
0
∞
∑
k
=
0
2
n
(
-
1
)
k
2
k
+
1
z
4
n
+
2
4
n
+
2
=
1
4
arctan
z
log
1
+
z
1
-
z
,
|
z
|
<
1
{\ displaystyle \ sum _ {n = 0} ^ {\ infty} \ sum _ {k = 0} ^ {2n} {\ frac {(-1) ^ {k}} {2k + 1}} {\ frac {z ^ {4n + 2}} {4n + 2}} = {\ frac {1} {4}} \ arctan {z} \ log {\ frac {1 + z} {1-z}}, \ qquad | z | <1}
Binomiale koefficienter
∑
k
=
0
n
(
n
k
)
=
2
n
{\ displaystyle \ sum _ {k = 0} ^ {n} {n \ vælg k} = 2 ^ {n}}
∑
k
=
0
n
(
-
1
)
k
(
n
k
)
=
0
,
hvor
n
>
0
{\ displaystyle \ sum _ {k = 0} ^ {n} (- 1) ^ {k} {n \ vælg k} = 0, {\ text {hvor}} n> 0}
∑
k
=
0
n
(
k
m
)
=
(
n
+
1
m
+
1
)
{\ displaystyle \ sum _ {k = 0} ^ {n} {k \ vælg m} = {n + 1 \ vælg m + 1}}
∑
k
=
0
n
(
m
+
k
-
1
k
)
=
(
n
+
m
n
)
{\ displaystyle \ sum _ {k = 0} ^ {n} {m + k-1 \ vælg k} = {n + m \ vælg n}}
(se Multiset )
∑
k
=
0
n
(
a
k
)
(
β
n
-
k
)
=
(
a
+
β
n
)
{\ displaystyle \ sum _ {k = 0} ^ {n} {\ alpha \ vælg k} {\ beta \ vælg nk} = {\ alpha + \ beta \ vælg n}}
(se Vandermonde identitet )
Trigonometriske funktioner
Sommer af sines og cosinus opstår i Fourier-serien .
∑
k
=
1
∞
cos
(
k
θ
)
k
=
-
1
2
ln
(
2
-
2
cos
θ
)
=
-
ln
(
2
synd
θ
2
)
,
0
<
θ
<
2
π
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {\ cos (k \ theta)} {k}} = - {\ frac {1} {2}} \ ln (2-2 \ cos \ theta) = - \ ln \ left (2 \ sin {\ frac {\ theta} {2}} \ right), 0 <\ theta <2 \ pi}
∑
k
=
1
∞
synd
(
k
θ
)
k
=
π
-
θ
2
,
0
<
θ
<
2
π
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {\ sin (k \ theta)} {k}} = {\ frac {\ pi - \ theta} {2}}, 0 < \ theta <2 \ pi}
∑
k
=
1
∞
(
-
1
)
k
-
1
k
cos
(
k
θ
)
=
1
2
ln
(
2
+
2
cos
θ
)
=
ln
(
2
cos
θ
2
)
,
0
≤
θ
<
π
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1}} {k}} \ cos (k \ theta) = {\ frac {1} { 2}} \ ln (2 + 2 \ cos \ theta) = \ ln \ left (2 \ cos {\ frac {\ theta} {2}} \ right), 0 \ leq \ theta <\ pi}
∑
k
=
1
∞
(
-
1
)
k
-
1
k
synd
(
k
θ
)
=
θ
2
,
-
π
2
≤
θ
≤
π
2
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {(-1) ^ {k-1}} {k}} \ sin (k \ theta) = {\ frac {\ theta} {2}}, - {\ frac {\ pi} {2}} \ leq \ theta \ leq {\ frac {\ pi} {2}}}
∑
k
=
1
∞
cos
(
2
k
θ
)
2
k
=
-
1
2
ln
(
2
synd
θ
)
,
0
<
θ
<
π
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {\ cos (2k \ theta)} {2k}} = - {\ frac {1} {2}} \ ln (2 \ sin \ theta), 0 <\ theta <\ pi}
∑
k
=
1
∞
synd
(
2
k
θ
)
2
k
=
π
-
2
θ
4
,
0
<
θ
<
π
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {\ sin (2k \ theta)} {2k}} = {\ frac {\ pi -2 \ theta} {4}}, 0 <\ theta <\ pi}
∑
k
=
0
∞
cos
[
(
2
k
+
1
)
θ
]
2
k
+
1
=
1
2
ln
(
barneseng
θ
2
)
,
0
<
θ
<
π
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {\ cos [(2k + 1) \ theta]} {2k + 1}} = {\ frac {1} {2}} \ ln \ left (\ cot {\ frac {\ theta} {2}} \ right), 0 <\ theta <\ pi}
∑
k
=
0
∞
synd
[
(
2
k
+
1
)
θ
]
2
k
+
1
=
π
4
,
0
<
θ
<
π
{\ displaystyle \ sum _ {k = 0} ^ {\ infty} {\ frac {\ sin [(2k + 1) \ theta]} {2k + 1}} = {\ frac {\ pi} {4}} , 0 <\ theta <\ pi}
,
∑
k
=
1
∞
synd
(
2
π
k
x
)
k
=
π
(
1
2
-
{
x
}
)
,
x
∈
R
{\ displaystyle \ sum _ {k = 1} ^ {\ infty} {\ frac {\ sin (2 \ pi kx)} {k}} = \ pi \ left ({\ dfrac {1} {2}} - \ {x \} \ højre), \ x \ i \ mathbb {R}}
∑
k
=
1
∞
synd
(
2
π
k
x
)
k
2
n
-
1
=
(
-
1
)
n
(
2
π
)
2
n
-
1
2
(
2
n
-
1
)
!
B
2
n
-
1
(
{
x
}
)
,
x
∈
R
,
n
∈
N
{\ displaystyle \ sum \ limits _ {k = 1} ^ {\ infty} {\ frac {\ sin \ left (2 \ pi kx \ right)} {k ^ {2n-1}}} = (- 1) ^ {n} {\ frac {(2 \ pi) ^ {2n-1}} {2 (2n-1)!}} B_ {2n-1} (\ {x \}), \ x \ in \ mathbb {R}, \ n \ in \ mathbb {N}}
∑
k
=
1
∞
cos
(
2
π
k
x
)
k
2
n
=
(
-
1
)
n
-
1
(
2
π
)
2
n
2
(
2
n
)
!
B
2
n
(
{
x
}
)
,
x
∈
R
,
n
∈
N
{\ displaystyle \ sum \ limits _ {k = 1} ^ {\ infty} {\ frac {\ cos \ left (2 \ pi kx \ right)} {k ^ {2n}}} = (- 1) ^ { n-1} {\ frac {(2 \ pi) ^ {2n}} {2 (2n)!}} B_ {2n} (\ {x \}), \ x \ in \ mathbb {R}, \ n \ in \ mathbb {N}}
B
n
(
x
)
=
-
n
!
2
n
-
1
π
n
∑
k
=
1
∞
1
k
n
cos
(
2
π
k
x
-
π
n
2
)
,
0
<
x
<
1
{\ displaystyle B_ {n} (x) = - {\ frac {n!} {2 ^ {n-1} \ pi ^ {n}}} \ sum _ {k = 1} ^ {\ infty} {\ frac {1} {k ^ {n}}} \ cos \ left (2 \ pi kx - {\ frac {\ pi n} {2}} \ right), 0 <x <1}
∑
k
=
0
n
synd
(
θ
+
k
a
)
=
synd
(
n
+
1
)
a
2
synd
(
θ
+
n
a
2
)
synd
a
2
{\ displaystyle \ sum _ {k = 0} ^ {n} \ sin (\ theta + k \ alpha) = {\ frac {\ sin {\ frac {(n + 1) \ alpha} {2}} \ sin (\ theta + {\ frac {n \ alpha} {2}})} {\ sin {\ frac {\ alpha} {2}}}}}
∑
k
=
0
n
cos
(
θ
+
k
a
)
=
synd
(
n
+
1
)
a
2
cos
(
θ
+
n
a
2
)
synd
a
2
{\ displaystyle \ sum _ {k = 0} ^ {n} \ cos (\ theta + k \ alpha) = {\ frac {\ sin {\ frac {(n + 1) \ alpha} {2}} \ cos (\ theta + {\ frac {n \ alpha} {2}})} {\ sin {\ frac {\ alpha} {2}}}}}
∑
k
=
1
n
-
1
synd
π
k
n
=
barneseng
π
2
n
{\ displaystyle \ sum _ {k = 1} ^ {n-1} \ sin {\ frac {\ pi k} {n}} = \ cot {\ frac {\ pi} {2n}}}
∑
k
=
1
n
-
1
synd
2
π
k
n
=
0
{\ displaystyle \ sum _ {k = 1} ^ {n-1} \ sin {\ frac {2 \ pi k} {n}} = 0}
∑
k
=
0
n
-
1
csc
2
(
θ
+
π
k
n
)
=
n
2
csc
2
(
n
θ
)
{\ displaystyle \ sum _ {k = 0} ^ {n-1} \ csc ^ {2} \ left (\ theta + {\ frac {\ pi k} {n}} \ right) = n ^ {2} \ csc ^ {2} (n \ theta)}
∑
k
=
1
n
-
1
csc
2
π
k
n
=
n
2
-
1
3
{\ displaystyle \ sum _ {k = 1} ^ {n-1} \ csc ^ {2} {\ frac {\ pi k} {n}} = {\ frac {n ^ {2} -1} {3 }}}
∑
k
=
1
n
-
1
csc
4
π
k
n
=
n
4
+
10
n
2
-
11
45
{\ displaystyle \ sum _ {k = 1} ^ {n-1} \ csc ^ {4} {\ frac {\ pi k} {n}} = {\ frac {n ^ {4} + 10n ^ {2 } -11} {45}}}
Rationelle funktioner
∑
n
=
-en
+
1
∞
-en
n
2
-
-en
2
=
1
2
H
2
-en
{\ displaystyle \ sum _ {n = a + 1} ^ {\ infty} {\ frac {a} {n ^ {2} -a ^ {2}}} = {\ frac {1} {2}} H_ {2a}}
∑
n
=
0
∞
1
n
2
+
-en
2
=
1
+
-en
π
coth
(
-en
π
)
2
-en
2
{\ displaystyle \ sum _ {n = 0} ^ {\ infty} {\ frac {1} {n ^ {2} + a ^ {2}}} = {\ frac {1 + a \ pi \ coth (a \ pi)} {2a ^ {2}}}}
∑
n
=
0
∞
1
n
4
+
4
-en
4
=
1
8
-en
4
+
π
(
sinh
(
2
π
-en
)
+
synd
(
2
π
-en
)
)
8
-en
3
(
koselig
(
2
π
-en
)
-
cos
(
2
π
-en
)
)
{\ displaystyle \ displaystyle \ sum _ {n = 0} ^ {\ infty} {\ frac {1} {n ^ {4} + 4a ^ {4}}} = {\ dfrac {1} {8a ^ {4 }}} + {\ dfrac {\ pi (\ sinh (2 \ pi a) + \ sin (2 \ pi a))} {8a ^ {3} (\ cosh (2 \ pi a) - \ cos (2 \ pi a))}}}
En uendelig række af enhver rationel funktion af kan reduceres til et endeligt række polygamma funktioner , ved brug af partiel fraktion nedbrydning . Denne kendsgerning kan også anvendes til begrænsede serier af rationelle funktioner, hvilket gør det muligt at beregne resultatet i konstant tid, selv når serien indeholder et stort antal udtryk.
n
{\ displaystyle n}
Eksponentiel funktion
1
s
∑
n
=
0
s
-
1
eksp
(
2
π
jeg
n
2
q
s
)
=
e
π
jeg
/
4
2
q
∑
n
=
0
2
q
-
1
eksp
(
-
π
jeg
n
2
s
2
q
)
{\ displaystyle \ displaystyle {\ dfrac {1} {\ sqrt {p}}} \ sum _ {n = 0} ^ {p-1} \ exp \ left ({\ frac {2 \ pi in ^ {2} q} {p}} \ right) = {\ dfrac {e ^ {\ pi i / 4}} {\ sqrt {2q}}} \ sum _ {n = 0} ^ {2q-1} \ exp \ left (- {\ frac {\ pi i ^ {2} p} {2q}} \ højre)}
(se forholdet Landsberg-Schaar )
∑
n
=
-
∞
∞
e
-
π
n
2
=
π
4
Γ
(
3
4
)
{\ displaystyle \ displaystyle \ sum _ {n = - \ infty} ^ {\ infty} e ^ {- \ pi n ^ {2}} = {\ frac {\ sqrt [{4}] {\ pi}} { \ Gamma \ left ({\ frac {3} {4}} \ right)}}
Se også
Bemærkninger
Referencer
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