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 A214691 #4 Jul 26 2012 00:23:01
%S A214691 1,1,5,151,19025,9702751,19851828545,162586475783551,
%T A214691 5327308465523832065,698250320576208668759551,
%U A214691 366082867573618138109269955585,767730685732013278335855487355082751,6440190236715680978727827356359771295535105
%N A214691 G.f.: A(x) = Sum_{n>=0} x^n * Product_{k=1..n} (2^(2*k-1) - 1) / (1 + 2^(2*k-1)*x).
%C A214691 A variant of A005014. Equals row sums (unsigned) of triangle A214690.
%F A214691 a(n) = 2*(4^(n-1) - 1)*a(n-1) - (-1)^n for n>0 with a(0)=1.
%o A214691 (PARI) {a(n)=if(n==0,1,2*(4^(n-1)-1)*a(n-1) - (-1)^n)}
%o A214691 (PARI) {a(n)=local(A=x); A=sum(m=0, n, x^m*prod(j=1, m, (2^(2*j-1)-1)/(1+x*2^(2*j-1))+x*O(x^n))); polcoeff(A, n, x)}
%o A214691 for(n=0, 20, print1(a(n), ", "));
%Y A214691 Cf. A005014 (variant), A214690.
%K A214691 nonn
%O A214691 0,3
%A A214691 _Paul D. Hanna_, Jul 26 2012