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 A144906 #3 Jan 21 2014 12:30:22 %S A144906 1,3,31,1684,271776,97484904,65617109160,74248657560720, %T A144906 130752443907524880,338450307621257099520,1232284889962378714855680, %U A144906 6094200542431309662145478400,39788645361978802435089535468800,334957784448996146804912925763507200 %N A144906 a(0) = 1; thereafter a(n) = A144422(n)/n. %Y A144906 Cf. A144422, A001515, A105749, A144905. %K A144906 nonn %O A144906 0,2 %A A144906 _David Applegate_ and _N. J. A. Sloane_, Feb 16 2009