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 A050491 #20 Jul 08 2023 04:03:09
%S A050491 1,13,50,185,686,2562,9636,36465,138710,529958,2032316,7818538,
%T A050491 30161740,116635300,451980360,1754766945,6824030310,26577181950,
%U A050491 103647597900,404703270510,1581953021220,6189965556060,24242879364600,95027512981050,372782298576636,1463445866837052
%N A050491 a(n) = C(n)*(12n+1) where C(n) = Catalan numbers (A000108).
%D A050491 Albert H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
%H A050491 Andrew Howroyd, <a href="/A050491/b050491.txt">Table of n, a(n) for n = 0..200</a>
%F A050491 G.f.: (11 - 20*x - 11*sqrt(1 - 4*x))/(2*x*sqrt(1 - 4*x)). - _Amiram Eldar_, Jul 08 2023
%t A050491 Table[CatalanNumber[n] * (12*n + 1), {n, 0, 25}] (* _Amiram Eldar_, Jul 08 2023 *)
%o A050491 (Magma) [Catalan(n)*(12*n+1):n in [0..25] ]; // _Marius A. Burtea_, Jan 05 2020
%Y A050491 Column k=12 of A330965.
%Y A050491 Cf. A017401, A027810, A000108.
%K A050491 easy,nonn
%O A050491 0,2
%A A050491 _Barry E. Williams_, Dec 27 1999
%E A050491 Terms a(21) and beyond from _Andrew Howroyd_, Jan 05 2020