OFFSET
0,3
EXAMPLE
E.g.f.: A(x) = 1 + x + 3*x^2/2! + 13*x^3/3! + 109*x^4/4! +...
A(x) = 1 + (1+x)*x + (1+x)^4*x^2/2! + (1+x)^9*x^3/3! + (1+x)^16*x^4/4! +...
MATHEMATICA
With[{nn=20}, CoefficientList[Series[Sum[(1+x)^n^2 x^n/n!, {n, 0, nn}], {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jul 28 2021 *)
PROG
(PARI) {a(n)=n!*polcoeff(sum(m=0, n, x^m*(1+x+x*O(x^n))^(m^2)/m!), n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 12 2011
STATUS
approved