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 A071897 #11 Feb 25 2017 04:52:54
%S A071897 1,3,16,227,9550,1260827,540904333,773494457017,3760730590920987,
%T A071897 63165231778603354669,3713231319097707398492821,
%U A071897 772396673211317543153892036521,573813488532401034128124101329943721,1534629746271367018386831539104008577227761
%N A071897 CONTINUANT transform of Catalan numbers 1, 2, 5, 14, 42, ...
%H A071897 Alois P. Heinz, <a href="/A071897/b071897.txt">Table of n, a(n) for n = 1..50</a>
%H A071897 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a>
%p A071897 a:= proc(n) option remember; `if`(n<0, 0,
%p A071897 `if`(n=0, 1, binomial(2*n, n)/(n+1) *a(n-1) +a(n-2)))
%p A071897 end:
%p A071897 seq(a(n), n=1..20); # _Alois P. Heinz_, Aug 06 2013
%t A071897 a[n_] := a[n] = If[n<0, 0, If[n==0, 1, CatalanNumber[n]*a[n-1] + a[n-2]]]; Table[a[n], {n, 1, 20}] (* _Jean-François Alcover_, Feb 25 2017, translated from Maple *)
%K A071897 nonn
%O A071897 1,2
%A A071897 _N. J. A. Sloane_, Jun 10 2002