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 A107087 #7 May 05 2014 01:25:39
%S A107087 1,2,-1,2,-5,12,-30,82,-233,668,-1949,5802,-17503,53302,-163783,
%T A107087 507418,-1582869,4966790,-15667573,49658264,-158059506,505013014,
%U A107087 -1619144976,5207596574,-16797286048,54323516786,-176113786590,572236347200,-1863213388504,6078422747600,-19865661574555
%N A107087 G.f. A(x) satisfies: A(x)^2 = A(x^2) + 4*x.
%C A107087 Self-convolution of A107086. Self-convolution yields A107088.
%F A107087 G.f. A(x) satisfies 0=f(A(x), A(x^2), A(x^4)) where f(u, v, w) = u^4 + 4*w - 2*u^2*v - 3*v^2. - _Michael Somos_, May 15 2005
%e A107087 A(x)^2 = 1 + 4*x + 2*x^2 - x^4 + 2*x^6 - 5*x^8 + 12*x^10 - 30*x^12 +...
%e A107087 A(x^2) = 1 + 2*x^2 - x^4 + 2*x^6 - 5*x^8 + 12*x^10 - 30*x^12 +...
%o A107087 (PARI) {a(n)=local(A=1+x);for(i=1,n,A=(subst(A,x,x^2)+4*x+x*O(x^n))^(1/2)); polcoeff(A,n,x)}
%o A107087 (PARI) {a(n)=local(m,A); if(n<0,0, A=1+O(x); m=1; while(m<=n, A=sqrt(4*x+subst(A,x,x^2));m*=2); polcoeff(A,n))} /* _Michael Somos_, May 15 2005 */
%Y A107087 Cf. A107086, A107088.
%K A107087 sign
%O A107087 0,2
%A A107087 _Paul D. Hanna_, May 11 2005