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 A276923 #11 Jun 13 2018 03:35:23
%S A276923 1,2,42,860,21490,657972,24011988,1017804216,49118959890,
%T A276923 2657929522820,159340977018652,10480673825750856,750335572490293972,
%U A276923 58077997318270046600,4832536579295065540200,430136064463753547944560,40779223639911413185024530
%N A276923 Number of ordered set partitions of [2n] where the maximal block size equals n.
%H A276923 Alois P. Heinz, <a href="/A276923/b276923.txt">Table of n, a(n) for n = 0..347</a>
%F A276923 a(n) = A276922(2n,n).
%F A276923 a(n) ~ 2^(2*n-3/2) * n^(n+1) / (exp(n) * log(2)^(n+2)). - _Vaclav Kotesovec_, Sep 24 2016
%p A276923 A:= proc(n, k) option remember; `if`(n=0, 1, add(
%p A276923 A(n-i, k)*binomial(n, i), i=1..min(n, k)))
%p A276923 end:
%p A276923 a:= n-> A(2*n, n) -`if`(n=0, 0, A(2*n, n-1)):
%p A276923 seq(a(n), n=0..20);
%t A276923 A[n_, k_] := A[n, k] = If[n == 0, 1, Sum[A[n - i, k]*Binomial[n, i], {i, 1, Min[n, k]}]];
%t A276923 a[n_] := A[2*n, n] - If[n == 0, 0, A[2*n, n - 1]];
%t A276923 Table[a[n], {n, 0, 20}] (* _Jean-François Alcover_, Jun 13 2018, translated from Maple *)
%Y A276923 Cf. A276922, A276961.
%K A276923 nonn
%O A276923 0,2
%A A276923 _Alois P. Heinz_, Sep 22 2016