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 A064991 #5 Mar 29 2014 09:05:43 %S A064991 0,1,78,20487601,369071811667060977001038, %T A064991 2157596228176369025492751451130809592490957353466093604326704974092869041 %N A064991 In A064990, drop leading 0's from A_k (for k>0) and convert to decimal. %C A064991 Next term is about 4.31*10^218. %F A064991 a(n+1) = a(n)(4^3^n + 2^3^n - 1) + 2^3^n - 1. - _David Wasserman_, Aug 20 2002 %K A064991 nonn,easy,base %O A064991 0,3 %A A064991 Michael Gilleland (megilleland(AT)yahoo.com), Oct 31 2001 %E A064991 More terms from _David Wasserman_, Aug 20 2002