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 A120796 #2 Mar 31 2012 13:20:12 %S A120796 1,20,200,1600,80000,1600000,16000000,1280000000,512000000, %T A120796 256000000000,2560000000000,102400000000000,1024000000000000, %U A120796 4096000000000000,40960000000000000,6553600000000000000 %N A120796 Denominators of partial sums of Catalan numbers scaled by powers of -1/20. %C A120796 Numerators are given under A120791. %F A120796 a(n)=denominator(r(n)), with the rationals r(n):=sum(((-1)^k)*C(k)/20^k,k=0..n) with C(k):=A000108(k) (Catalan numbers). Rationals r(n) are taken in lowest terms. %K A120796 nonn,easy,frac %O A120796 0,2 %A A120796 _Wolfdieter Lang_, Jul 20 2006