A210244 - OEIS

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A210244

Numerators of the polylogarithm li(-n,-1/2)/2.

-1, -1, 1, 5, -7, -49, -53, 2215, 1259, -14201, -183197, 248885, 9583753, 14525053, -554173253, -4573299625, 99833187251, 215440236599, -1654012631597, -84480933600305, -36267273557287, 10992430255511053, 117548575473066241, -1380910044674479865

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OFFSET

1,4

COMMENTS

Given an integer n>0, consider the infinite series s(n) = li(-n,-1/2) = Sum_{k>=1} (-1)^k*k^n/2^k. Then s(n)=2*a(n)/A131137(n+1).

LINKS

Table of n, a(n) for n=1..24.

S. Sykora, Finite and Infinite Sums of the Power Series (k^p)(x^k), Stan's Library Vol.I, April 2006, updated March 2012. See Eq.(29).

Eric W. Weisstein, MathWorld: Polylogarithm

FORMULA

Recurrence: s(n+1)=(-1/3)*Sum_{i=0..n} binomial(n+1,i)*s(i), with the starting value of s(0)=2/3.

EXAMPLE

s(1)=-2/9, s(2)=-2/27, s(3)=+2/27, s(4)=+10/81.

MATHEMATICA

nn = 30; s[0] = 1; Do[s[n+1] = (-1/3) Sum[Binomial[n+1, i] s[i], {i, 0, n}], {n, 0, nn}]; Numerator[Table[s[n], {n, 0, nn}]] (* T. D. Noe, Mar 20 2012 *)

Table[PolyLog[-n, -1/2]/2, {n, 30}] (* T. D. Noe, Mar 23 2012 *)

PROG

(PARI) a(n)=numerator(polylog(-n, -1/2)/2) \\ Charles R Greathouse IV, Jul 15 2014

CROSSREFS

Denominators: A131137, offset by 1.

Cf. A212846.

Sequence in context: A217039 A299452 A110420 * A123789 A367572 A180552

Adjacent sequences: A210241 A210242 A210243 * A210245 A210246 A210247

KEYWORD

sign,frac

AUTHOR

Stanislav Sykora, Mar 19 2012

STATUS

approved