A293848 - OEIS

%I #18 Oct 18 2017 11:46:55

%S 1,1,9,187,7033,421341,37025881,4500154639,723834652017,

%T 148905928574713,38133707320119241,11894979981772431171,

%U 4439223538343665367209,1952818695816854110909717,999887879061130705615605273,589500991222520435444933020951

%N E.g.f.: exp(Sum_{n>=1} n^n*x^n).

%H Seiichi Manyama, <a href="/A293848/b293848.txt">Table of n, a(n) for n = 0..232</a>

%F a(0) = 1 and a(n) = (n-1)! * Sum_{k=1..n} k^(k+1)*a(n-k)/(n-k)! for n > 0.

%F a(n) ~ n! * n^n. - _Vaclav Kotesovec_, Oct 18 2017

%t nmax = 20; CoefficientList[Series[E^Sum[k^k*x^k, {k, 1, nmax}], {x, 0, nmax}], x] * Range[0, nmax]! (* _Vaclav Kotesovec_, Oct 18 2017 *)

%o (PARI) {a(n) = n!*polcoeff(exp(sum(k=1, n, k^k*x^k)+x*O(x^n)), n)}

%Y Cf. A293847, A293849.

%K nonn

%O 0,3

%A _Seiichi Manyama_, Oct 17 2017