This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A187658 #15 May 31 2025 08:02:46
%S A187658 1,2,24,516,16064,655840,33157240,1999679696,140128848384,
%T A187658 11189643689088,1003005057594240,99725721676986240,
%U A187658 10892178742891589792,1296379044138734510656,166999512859041432577280,23149972436862049305233280
%N A187658 Binomial convolution of the (signless) central Stirling numbers of the first kind (A187646).
%F A187658 a(n) = Sum_{k=0..n} binomial(n,k)*s(2*k,k)*s(2*n-2*k,n-k).
%F A187658 Limit_{n->oo} (a(n)/n!)^(1/n) = -8*LambertW(-1, -exp(-1/2)/2)^2 / (1 + 2*LambertW(-1, -exp(-1/2)/2)) = 9.821629929136511797503... - _Vaclav Kotesovec_, May 30 2025
%p A187658 seq(sum(binomial(n,k)*abs(combinat[stirling1](2*k,k))*abs(combinat[stirling1](2*(n-k),n-k)),k=0..n),n=0..12);
%t A187658 Table[Sum[Binomial[n, k]Abs[StirlingS1[2k, k]]Abs[StirlingS1[2n - 2k, n - k]], {k, 0, n}], {n, 0, 15}]
%o A187658 (Maxima) makelist(sum(binomial(n,k)*abs(stirling1(2*k,k))*abs(stirling1(2*n-2*k,n-k)),k,0,n),n,0,12);
%Y A187658 Cf. A187646, A384495, A384496.
%K A187658 nonn,easy
%O A187658 0,2
%A A187658 _Emanuele Munarini_, Mar 12 2011