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 A187542 #11 Oct 06 2019 07:27:30
%S A187542 1,4,76,2544,123696,7942080,635633280,61009159680,6831940227840,
%T A187542 874493448514560,125946241018214400,20156433977646489600,
%U A187542 3548609812373223628800,681555522002874494976000,141810253720479017017344000
%N A187542 Convolutions of the central Lah numbers (A187535).
%H A187542 Vaclav Kotesovec, <a href="/A187542/b187542.txt">Table of n, a(n) for n = 0..300</a>
%F A187542 a(n) = sum(L(k)L(n-k),k=0..n), where L(n) is a central Lah number.
%F A187542 a(n) ~ n! * 16^n / (Pi*n). - _Vaclav Kotesovec_, Oct 06 2019
%p A187542 a := n -> if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n! fi;
%p A187542 seq(sum(a(k)*a(n-k), k=0..n),n=0..12);
%t A187542 a[n_] := If[n == 0, 1, Binomial[2n - 1, n - 1](2n)!/n!]
%t A187542 Table[Sum[a[k]a[n - k], {k, 0, n}], {n, 0, 20}]
%o A187542 (Maxima) a(n) := if n=0 then 1 else binomial(2*n-1,n-1)*(2*n)!/n!;
%o A187542 makelist(sum(a(k)*a(n-k),k,0,n),n,0,12);
%Y A187542 Cf. A187536, A008297, A111596, A187536, A187538, A187539, A187540, A187543, A187544, A187545, A187546, A187547, A187548.
%K A187542 nonn,easy
%O A187542 0,2
%A A187542 _Emanuele Munarini_, Mar 11 2011