OFFSET
0,7
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..10000
FORMULA
MATHEMATICA
nmax = 100; CoefficientList[Series[Sum[n*x^(n*(n+1))*Product[1+x^k, {k, 1, n}], {n, 0, Sqrt[nmax]}], {x, 0, nmax}], x]
nmax = 100; p = 1; s = 0; Do[p = Expand[p*(1 + x^k)*x^(2*k)]; p = Take[p, Min[nmax + 1, Exponent[p, x] + 1, Length[p]]]; s += k*p; , {k, 1, Sqrt[nmax]}]; Take[CoefficientList[s, x], nmax + 1]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Mar 10 2020
STATUS
approved