OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
FORMULA
Dirichlet convolution of A072861 and A000012. Dirichlet g.f.: zeta^2(s)*zeta^2(s-1)*zeta(s-2)/zeta(2s-2). - R. J. Mathar, Feb 03 2011
Sum_{k=1..n} a(k) ~ 5 * Zeta(3)^2 * n^3 / 6. - Vaclav Kotesovec, Feb 01 2019
From Seiichi Manyama, May 08 2021: (Start)
G.f.: Sum_{k >= 1} sigma(k)^2 * x^k/(1 - x^k).
If p is prime, a(p) = 1 + (p+1)^2. (End)
PROG
(PARI) { for (n=1, 1000, a=sumdiv(n, d, sigma(d)^2); write("b065018.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 03 2009
(PARI) my(N=66, x='x+O('x^N)); Vec(sum(k=1, N, sigma(k)^2*x^k/(1-x^k))) \\ Seiichi Manyama, May 08 2021
CROSSREFS
KEYWORD
mult,nonn
AUTHOR
Vladeta Jovovic, Nov 19 2001
STATUS
approved