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a(n) = Sum_{k=0..n} k! * k^(2*n) * Stirling1(n,k).
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%I #27 Feb 06 2022 02:15:25

%S 1,1,31,3992,1342294,932514674,1161340476698,2356863300156504,

%T 7278091701243797640,32477694155566998880608,

%U 201155980661221409458717152,1674230688936725338278370413264,18235249164492209082483584810706528

%N a(n) = Sum_{k=0..n} k! * k^(2*n) * Stirling1(n,k).

%H Seiichi Manyama, <a href="/A351133/b351133.txt">Table of n, a(n) for n = 0..162</a>

%F E.g.f.: Sum_{k>=0} log(1 + k^2*x)^k.

%F a(n) ~ c * d^n * n^(3*n + 1/2), where d = 0.3417329834649268103028466896966197580428514873775849996969994420891... and c = 2.92355271092039591960355156784704285135358... - _Vaclav Kotesovec_, Feb 03 2022

%t a[0] = 1; a[n_] := Sum[k! * k^(2*n) * StirlingS1[n, k], {k, 1, n}]; Array[a, 13, 0] (* _Amiram Eldar_, Feb 02 2022 *)

%o (PARI) a(n) = sum(k=0, n, k!*k^(2*n)*stirling(n, k, 1));

%o (PARI) first(n)=my(x='x+O('x^(n+1))); Vec(serlaplace(sum(k=0, n, log(1+k^2*x)^k)))

%Y Cf. A006252, A320083, A351134.

%Y Cf. A229260, A351135, A351136.

%K nonn

%O 0,3

%A _Seiichi Manyama_, Feb 02 2022