OFFSET
1,2
FORMULA
a(n) ~ zeta(3) * n * 4^(n-1).
MATHEMATICA
Table[Sum[Binomial[2*n, n-k]*DivisorSigma[2, k], {k, 1, n}], {n, 1, 30}]
PROG
(PARI) a(n) = sum(k=1, n, binomial(2*n, n-k) * sigma(k, 2)); \\ Michel Marcus, Aug 05 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Aug 04 2022
STATUS
approved