OFFSET
0,3
COMMENTS
Multiplicative because A000203 is. - Andrew Howroyd, Jul 25 2018
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
Joerg Arndt, On computing the generalized Lambert series, arXiv:1202.6525v3 [math.CA], (2012).
FORMULA
G.f.: phi_{4, 3}(x) where phi_{r, s}(x) = Sum_{n, m>0} m^r * n^s * x^{m*n}.
a(n) = n^3*A000203(n) for n > 0. - Seiichi Manyama, Feb 19 2017
G.f.: A(q) = Sum_{n >= 1} n^3*q^n*(q^(3*n) + 11*q^(2*n) + 11*q^n + 1)/(1 - q^n)^5. A faster converging series may be found by applying the operator x*d/dx once to equation 5 in Arndt, setting x = 1, and then applying the operator q*d/dq three times to the resulting equation. - Peter Bala, Jan 21 2021
Sum_{k=1..n} a(k) ~ c * n^5, where c = Pi^2/30 = 0.328986... . - Amiram Eldar, Dec 08 2022
From Amiram Eldar, Oct 31 2023: (Start)
Multiplicative with a(p^e) = p^(3*e) * (p^(e+1)-1)/(p-1).
Dirichlet g.f.: zeta(s-3)*zeta(s-4). (End)
G.f.: A(q) = Sum_{n >= 1} n^4*q^n*(q^(2*n) + 4*q^n + 1)/(1 - q^n)^4. - Mamuka Jibladze, Aug 27 2024
EXAMPLE
a(6) = 1^4*6^3 + 2^4*3^3 + 3^4*2^3 + 6^4*1^3 = 2592.
MATHEMATICA
a[0]=0; a[n_]:=(n^3)*DivisorSigma[1, n]; Table[a[n], {n, 0, 33}] (* Indranil Ghosh, Feb 21 2017 *)
PROG
(PARI) a(n) = if (n==0, 0, n^3*sigma(n)); \\ Michel Marcus, Feb 21 2017
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
Seiichi Manyama, Feb 09 2017
STATUS
approved