OFFSET
1,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..10000
FORMULA
a(4n+2) = 0.
a(2n+1) = A034715(2n+1), where A034715 is the Dirichlet convolution of triangular numbers with themselves.
a(n) = (n/4) * Sum_{d|n} (-1)^(n+d) * (d+1) * (n/d+1). - Seiichi Manyama, Jul 17 2023
MATHEMATICA
CoefficientList[Series[Sum[((k(k+1))/2 x^k)/(1-(-x)^k)^3, {k, 100}], {x, 0, 100}], x] (* Harvey P. Dale, May 08 2021 *)
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
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 06 2009
STATUS
approved