OFFSET
1,2
LINKS
Eric Weisstein's World of Mathematics, Divisor Function.
FORMULA
a(n) ~ zeta(3) * n^2 * 2^(n-2).
a(n) = Sum_{i=1..n} Sum_{j=1..n} (i^2)*binomial(n,i*j). - Ridouane Oudra, Oct 25 2022
MAPLE
with(numtheory): seq(add(sigma[2](i)*binomial(n, i), i=1..n), n=1..60); # Ridouane Oudra, Oct 25 2022
MATHEMATICA
Table[Sum[Binomial[n, k] * DivisorSigma[2, k], {k, 1, n}], {n, 1, 40}]
PROG
(PARI) a(n) = sum(k=1, n, binomial(n, k) * sigma(k, 2)); \\ Michel Marcus, Jul 24 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Jul 24 2022
STATUS
approved