OFFSET
0,3
FORMULA
Sum_{n>=0} a(n) * x^n / (n!)^2 = polylog(2,x) * exp(-x).
MATHEMATICA
Table[(n!)^2 Sum[(-1)^k/((n - k)^2 k!), {k, 0, n - 1}], {n, 0, 18}]
nmax = 18; CoefficientList[Series[PolyLog[2, x] Exp[-x], {x, 0, nmax}], x] Range[0, nmax]!^2
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, Jul 15 2021
STATUS
approved