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 A131710 #4 Mar 30 2012 18:51:52 %S A131710 0,1,2,5,12,29,70,170,410,990,2390,5770,13930,33630,81190,196010, %T A131710 473210,1142430,2758070,6658570,16075210,38808990,93693190,226195370, %U A131710 546083930,1318363230,3182810390,7683984010,18550778410,44785540830,108121860070 %N A131710 Overlay of Pell numbers: a(n)=A000129(n)+A000129(n-6). %F A131710 a(n)=A000129(n), n <=6. a(n)=10*A001333(n-3), n >=7. %F A131710 O.g.f.: x(1+x^2)(1-x^2+x^4)/(1-2x-x^2). - _R. J. Mathar_, Jul 07 2008. %K A131710 nonn %O A131710 0,3 %A A131710 _Paul Curtz_, Sep 14 2007 %E A131710 Edited by _R. J. Mathar_, Jul 07 2008