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%I #9 Mar 03 2026 08:18:37
%S 0,1,1,4,26,241,2947,45248,843732,18661671,481146211,14268787628,
%T 481575324194,18335512686481,781646971249603,37063676993936908,
%U 1943284729431092340,112059055358657319023,7072342296849963327347,486361147949618853157892
%N a(0) = 0, a(1) = 1; a(n) = n! * [x^n] (1/n)^2 * exp(n*x) * Sum_{k=1..n-1} a(k)*x^k/k!.
%F a(n) = Sum_{k=1..n-1} n^(k-2) * binomial(n,k) * a(n-k) for n > 1.
%Y Cf. A089918, A293860.
%K nonn
%O 0,4
%A _Seiichi Manyama_, Mar 03 2026