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 A187659 #13 May 28 2017 04:07:31
%S A187659 1,2,19,333,8862,322885,15061381,858280605,57766424400,4479377168841,
%T A187659 392785285842806,38393983653735732,4136603248470746422,
%U A187659 486806030644218961182,62109988002922704031388,8537900524822110186179616
%N A187659 Convolution of the (signless) central Stirling numbers of the first kind (A187646) and the central Stirling numbers of the second kind (A007820).
%H A187659 G. C. Greubel, <a href="/A187659/b187659.txt">Table of n, a(n) for n = 0..250</a>
%F A187659 a(n) = Sum_{k=0..n} s(2*k,k)*S(2*n-2*k,n-k).
%F A187659 a(n) ~ n^n * c^(2*n) * 2^(3*n-1) / (sqrt(Pi*(c-1)*n) * exp(n) * (2*c-1)^n), where c = -LambertW(-1,-exp(-1/2)/2). - _Vaclav Kotesovec_, May 21 2014
%p A187659 seq(sum(abs(combinat[stirling1](2*k,k))*combinat[stirling2](2*(n-k),n-k),k=0..n),n=0..12);
%t A187659 Table[Sum[Abs[StirlingS1[2k, k]]StirlingS2[2n - 2k, n - k], {k, 0, n}], {n, 0, 15}]
%o A187659 (Maxima) makelist(sum(abs(stirling1(2*k,k))*stirling2(2*n-2*k,n-k),k,0,n),n,0,12);
%o A187659 (PARI) a(n) = sum(k=0, n, abs(stirling(2*k, k, 1)*stirling(2*(n-k), n-k, 2))); \\ _Michel Marcus_, May 28 2017
%Y A187659 Cf. A007820, A187646.
%K A187659 nonn,easy
%O A187659 0,2
%A A187659 _Emanuele Munarini_, Mar 12 2011