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 A063017 #17 Jun 26 2018 13:02:58
%S A063017 1,3,20,165,1484,13986,135960,1352637,13707980,141061206,1470489800,
%T A063017 15500280978,164967244792,1770548369700,19143828730800,
%U A063017 208347968093085,2280730450967820,25096531231958670,277445318198433000
%N A063017 a(n) = Catalan(n)*(3^(n+1) - 2^(n+1) + 1)/2.
%H A063017 Harry J. Smith, <a href="/A063017/b063017.txt">Table of n, a(n) for n = 0..200</a>
%F A063017 a(n) = Catalan(n)*(3^(n+1) - 2^(n+1) + 1)/2;
%F A063017 o.g.f: -(sqrt(1-4x) - sqrt(1-8x)+ sqrt(1-12x) -1)/(4x).
%t A063017 Table[CatalanNumber[n] (3^(n + 1) - 2^(n + 1) + 1)/2, {n, 0, 20}] (* _Wesley Ivan Hurt_, Jan 30 2014 *)
%o A063017 (PARI) a(n)={binomial(2*n, n)/(n + 1)*(3^(n+1) - 2^(n+1) + 1)/2} \\ _Harry J. Smith_, Aug 16 2009
%Y A063017 Cf. A000108, A063016.
%K A063017 easy,nonn
%O A063017 0,2
%A A063017 _Olivier Gérard_, Jul 04 2001
%E A063017 Formula corrected by _Harry J. Smith_, Aug 16 2009