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 A056238 #2 Mar 30 2012 17:30:25 %S A056238 6,252,272,858,2772,4004,6006,289982,2370732,2629262,6039306,27999972, %T A056238 28233282,2704884072,20278187202,20591819502,2592587852952, %U A056238 2936231326392,21809166190812,27237788773272,229145919541922 %N A056238 Nontrivial palindromic denominators in Leibniz's harmonic triangle. %Y A056238 Cf. A007622. %K A056238 nonn,base %O A056238 1,1 %A A056238 _Robert G. Wilson v_, Aug 21 2000