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 A187664 #13 May 30 2025 04:54:15
%S A187664 1,3,49,1483,67615,4173203,326208269,30880075203,3430574739759,
%T A187664 437145190334383,62803806114813801,10038354053796477099,
%U A187664 1766255133182030548351,339166069936077378326187,70571377417819411767223541
%N A187664 Convolution of the (signless) central Lah numbers (A187535) and the (signless) central Stirling numbers of the first kind (A187646).
%F A187664 a(n) = Sum_{k=0..n} Lah(2*k,k)*s(2*n-2*k,n-k).
%F A187664 a(n) ~ 2^(4*n - 1/2) * n^(n - 1/2) / (sqrt(Pi) * exp(n)). - _Vaclav Kotesovec_, May 30 2025
%p A187664 L := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
%p A187664 seq(sum(L(k)*abs(combinat[stirling1](2*(n-k),n-k)),k=0..n),n=0..12);
%t A187664 L[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
%t A187664 Table[Sum[L[k]Abs[StirlingS1[2n - 2k, n - k]], {k, 0, n}], {n, 0, 14}]
%o A187664 (Maxima) L(n):= if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
%o A187664 makelist(sum(L(k)*abs(stirling1(2*n-2*k,n-k)),k,0,n),n,0,12);
%Y A187664 Cf. A187535, A187646.
%K A187664 nonn,easy
%O A187664 0,2
%A A187664 _Emanuele Munarini_, Mar 12 2011