OFFSET
0,2
FORMULA
a(n) ~ 2 * n! * (1 + 2/n + 6/n^2 + 28/n^3 + 162/n^4 + 1134/n^5 + 9368/n^6 + 89502/n^7 + 974338/n^8 + 11948360/n^9 + 163462518/n^10). - Vaclav Kotesovec, Sep 15 2017
MATHEMATICA
nmax = 25; CoefficientList[Series[Product[(1 + k!*x^k)/(1 - k!*x^k), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Sep 15 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 14 2017
STATUS
approved