OFFSET
1,3
COMMENTS
Convolution of tau with sigma_2.
FORMULA
G.f.: ( Sum_{k>=1} x^k/(1 - x^k) ) * ( Sum_{k>=1} k^2 * x^k/(1 - x^k) ).
PROG
(PARI) a(n) = sum(k=1, n-1, sigma(k, 0)*sigma(n-k, 2));
(PARI) my(N=50, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^k/(1-x^k))*sum(k=1, N, k^2*x^k/(1-x^k))))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Jul 26 2024
STATUS
approved