OFFSET
1,2
LINKS
P. Flajolet and R. Sedgewick, Analytic Combinatorics, 2009; page 139.
FORMULA
E.g.f.: log(Sum_{n>=0} n!^2*x^n).
a(n) = (n!)^3 - (n-1)! * Sum_{k=1..n-1} a(k) * ((n-k)!)^2 / (k-1)!. - Ilya Gutkovskiy, Jul 10 2020
MATHEMATICA
nn=14; b=Sum[n!^3 x^n/n!, {n, 0, nn}]; Drop[Range[0, nn]!CoefficientList[Series[Log[b], {x, 0, nn}], x], 1]
PROG
(PARI)
N = 66; x = 'x + O('x^N);
egf = log(sum(n=0, N, n!^2*x^n));
gf = serlaplace(egf);
v = Vec(gf)
/* Joerg Arndt, Apr 14 2013 */
CROSSREFS
KEYWORD
nonn
AUTHOR
Geoffrey Critzer, Apr 13 2013
STATUS
approved