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 A072563 #6 Mar 30 2012 18:39:03 %S A072563 9,9,9,15,23,51,93,225,429,1059,2039,5055,9753,24201,46713,115935, %T A072563 223799,555459,1072269,2661345,5137533,12751251,24615383,61094895, %U A072563 117939369,292723209,565081449,1402521135,2707467863,6719882451 %N A072563 9*w(n) where : w(1)=w(2)=w(3)=1 w(n)=(w(n-1)*w(n-2)+(w(n-1)+w(n-2))/3) / w(n-3). %C A072563 All terms are integers. %F A072563 lim n -> infinity a(n+1)/a(n) = (1/6) * ( 7 + sqrt(21) ) = 1.93042928249263... %F A072563 G.f.: x(15x^5+23x^4-39x^3-45x^2+9x+9)/(-x^6+6x^4-6x^2+1). %Y A072563 Cf. A072881, A072557, A072560, A072561. %K A072563 nonn %O A072563 1,1 %A A072563 _Benoit Cloitre_, Aug 06 2002