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 A267987 #19 Sep 08 2022 08:46:15
%S A267987 4,8,48,400,3920,42336,487872,5889312,73616400,945561760,12412647104,
%T A267987 165878102208,2249987591488,30906422960000,429157758816000,
%U A267987 6015361252737600,85011208292365200,1210159553338375200,17338543308064440000,249857534618318088000
%N A267987 a(n) = Catalan(n)^2*(4n + 4).
%C A267987 Numerator of the modified (4n+4) Wallis-Lambert series with denominator A013709 convergent to 4/Pi. Proof: Both the Wallis-Lambert-series-1=4/Pi-1 and the elliptic Euler-series=1-2/Pi are absolutely convergent series. Thus any linear combination of the terms of these series will be also absolutely convergent to the value of the linear combination of these series - in this case: 4/Pi. Q.E.D.
%t A267987 Table[CatalanNumber[n]^2 (4 n + 4), {n, 0, 20}] (* _Vincenzo Librandi_, Jan 24 2016 *)
%o A267987 (Magma) [Catalan(n)^2*(4*n+4):n in [0..30]]; // _Vincenzo Librandi_, Jan 24 2016
%Y A267987 Cf. A013709 (denominator).
%K A267987 nonn,easy,frac
%O A267987 0,1
%A A267987 _Ralf Steiner_, Jan 23 2016
%E A267987 More terms from _Vincenzo Librandi_, Jan 24 2016