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%I #26 Mar 24 2024 08:16:40
%S 1,2,8,38,228,1562,12386,109286,1073988,11545994,135393438,1714890806,
%T 23380747506,341014477390,5303722839850,87582446980418,
%U 1531259993710468,28254163132485930,548854481037814382,11196310379931318758,239346426732701009838,5350768890908294837294
%N Expansion of e.g.f. Product_{k>=1} 1 / (1 - x^k/k!)^2.
%C Exponential self-convolution of A005651.
%F a(n) = Sum_{k=0..n} binomial(n,k) * A005651(k) * A005651(n-k).
%F a(n) ~ A247551^2 * n! * n. - _Vaclav Kotesovec_, Mar 24 2024
%t nmax = 21; CoefficientList[Series[Product[1/(1 - x^k/k!)^2, {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]!
%Y Cf. A005651, A032312.
%K nonn
%O 0,2
%A _Ilya Gutkovskiy_, Mar 24 2024