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 A299428 #14 Feb 11 2019 02:54:12
%S A299428 1,4,63,1872,82775,4874688,358919022,31726703424,3273365223135,
%T A299428 386120802767700,51255818495200660,7561964058268969440,
%U A299428 1227474574989496660008,217398508335873934190800,41718377034325560258265500,8622580886584109407750765824,1909661474657747399115123743055,451173386162679212279972033149500
%N A299428 a(n) = binomial((n+1)*(2*n+1), n) * (n+1)/(2*n+1).
%C A299428 Main diagonal of square table A299427.
%H A299428 Seiichi Manyama, <a href="/A299428/b299428.txt">Table of n, a(n) for n = 0..310</a>
%F A299428 a(n) ~ 2^(n - 3/2) * exp(n + 5/4) * n^(n - 1/2) / sqrt(Pi). - _Vaclav Kotesovec_, Feb 19 2018
%o A299428 (PARI) {a(n) = binomial((n+1)*(2*n+1), n) * (n+1)/(2*n+1)}
%o A299428 for(n=0,20,print1(a(n),", "))
%Y A299428 Cf. A299427, A299429.
%K A299428 nonn
%O A299428 0,2
%A A299428 _Paul D. Hanna_, Feb 19 2018
%E A299428 a(15) corrected by _Seiichi Manyama_, Feb 10 2019