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 A097131 #4 Mar 30 2012 18:58:56 %S A097131 1,1,2,1,5,2,13,5,34,13,89,34,233,89,610,233,1597,610,4181,1597,10946, %T A097131 4181,28657,10946,75025,28657,196418,75025,514229,196418,1346269, %U A097131 514229,3524578,1346269,9227465,3524578,24157817,9227465,63245986,24157817 %N A097131 F(n)+(-1)^n*F(n-1). %F A097131 G.f. : x/(1-x-x^2)+(1+x)/(1+x-x^2)=(1+x-x^2-2x^3)/(1-3x^2+x^4); a(n)=3a(n-2)-a(n-4); a(2n)=F(2n+1); a(2n+1)=F(2n-1). %F A097131 a(n)=A087123(n-1), n>0. [From _R. J. Mathar_, Sep 02 2008] %Y A097131 Cf. A000045. %K A097131 easy,nonn %O A097131 0,3 %A A097131 _Paul Barry_, Jul 26 2004