OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
G.f.: Product_{k>=1} ((1 + x^k)/(1 - x^k))^A007426(k).
MATHEMATICA
With[{nmax=50}, CoefficientList[Series[Product[(1 + x^(i*j*k*l))/(1 - x^(i*j*k*l)), {i, 1, nmax}, {j, 1, nmax/i}, {k, 1, nmax/i/j}, {l, 1, nmax/i/j/k}], {x, 0, nmax}], x]] (* G. C. Greubel, Nov 01 2018 *)
PROG
(PARI) m=50; x='x+O('x^m); Vec(prod(k=1, m, ((1+x^k)/(1-x^k))^ sumdiv(k, d, numdiv(k/d)*numdiv(d)))) \\ G. C. Greubel, Nov 01 2018
(Magma) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!( (&*[(&*[(&*[(&*[(1+x^(i*j*k*l))/(1-x^(i*j*k*l)): i in [1..m]]): j in [1..m]]): k in [1..m]]): l in [1..m]]))); // G. C. Greubel, Nov 01 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Nov 01 2018
STATUS
approved