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 A120995 #5 Oct 02 2013 19:07:53 %S A120995 1,15,175,3675,14553,231231,920205,234652275,2807136475,14933966047, %T A120995 59612442981,11425718238025,15211755050625,243077636829375, %U A120995 971230202264925,993568496917018275,3970836034391543625 %N A120995 Denominators of rationals related to John Wallis' product formula for Pi/2 (from his 'Arithmetica infinitorum' from 1659). %C A120995 The corresponding numerators are A120994. %C A120995 The rationals W(n):= (((4^n)/binomial(2*n,n))^2)/(2*n+1) converge to Pi/2 = 1.570796327... %F A120995 a(n) = denominators((3/4)*W(n)), n>=1. %K A120995 nonn,easy,frac %O A120995 1,2 %A A120995 _Wolfdieter Lang_, Aug 01 2006