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 A055591 #6 Nov 21 2013 12:47:23 %S A055591 0,1,4,85,35917545547686059365808220080151141317128 %N A055591 a(n) = a(n-1)+3^a(n-1). %F A055591 a(n) = A055591(n-1)+A055590(n) %e A055591 a(3) = 4+3^4 = 4+81 = 85 %t A055591 NestList[#+3^#&,0,4] (* _Harvey P. Dale_, Apr 18 2012 *) %Y A055591 Cf. A034797, A055590. %K A055591 easy,nonn %O A055591 0,3 %A A055591 _Henry Bottomley_, May 26 2000