OFFSET
0,3
COMMENTS
Multiplicative because A001158 is. - Andrew Howroyd, Jul 25 2018
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: phi_{5, 2}(x) where phi_{r, s}(x) = Sum_{n, m>0} m^r * n^s * x^{m*n}.
a(n) = n^2*A001158(n) for n > 0. - Seiichi Manyama, Feb 19 2017
Sum_{k=1..n} a(k) ~ Pi^4 * n^6 / 540. - Vaclav Kotesovec, May 09 2022
From Amiram Eldar, Oct 30 2023: (Start)
Multiplicative with a(p^e) = p^(2*e) * (p^(3*e+3)-1)/(p^3-1).
Dirichlet g.f.: zeta(s-2)*zeta(s-5). (End)
EXAMPLE
a(6) = 1^5*6^2 + 2^5*3^2 + 3^5*2^2 + 6^5*1^2 = 9072.
MATHEMATICA
a[0]=0; a[n_]:=(n^2)*DivisorSigma[3, n]; Table[a[n], {n, 0, 32}] (* Indranil Ghosh, Feb 21 2017 *)
PROG
(PARI) a(n) = if (n==0, 0, n^2*sigma(n, 3)); \\ Michel Marcus, Feb 21 2017
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
Seiichi Manyama, Feb 06 2017
STATUS
approved