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A163920 G.f.: Sum_{k>0} k*(k+1)/2 * x^k / (1 - (-x)^k)^3. 0
1, 0, 12, 9, 30, 0, 56, 60, 126, 0, 132, 126, 182, 0, 420, 316, 306, 0, 380, 330, 798, 0, 552, 888, 875, 0, 1296, 630, 870, 0, 992, 1536, 1914, 0, 2100, 1467, 1406, 0, 2652, 2360, 1722, 0, 1892, 1518, 4860, 0, 2256, 4872, 3234, 0, 4488, 2106, 2862, 0, 5060 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..55.

FORMULA

a(4n+2) = 0.

a(2n+1) = A034715(2n+1), where A034715 is the Dirichlet convolution of triangular numbers with themselves.

PROG

(PARI) {a(n) = if( n<1, 0, polcoeff( sum(k=1, n, k*(k+1)/2 * x^k / (1 - (-x)^k)^3, x*O(x^n)), n))}

CROSSREFS

Cf. A143520 (variant), A034715.

Sequence in context: A018870 A327470 A068614 * A038335 A216856 A040023

Adjacent sequences:  A163917 A163918 A163919 * A163921 A163922 A163923

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Aug 06 2009

STATUS

approved

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Last modified June 6 14:04 EDT 2020. Contains 334827 sequences. (Running on oeis4.)