OFFSET
0,5
COMMENTS
G.f. A(x) satisfies 0=f(A(x),A(x^2)) where f(u,v)=u^2-v-2uv(1+v+uv).
PROG
(PARI) a(n)=local(A, m); if(n<0, 0, A=x+O(x^2); m=1; while(m<=n, m*=2; A=subst(A, x, x^2); A=(A+A^2+sqrt(A+A^2+A^4))/(1-2*A^2)); polcoeff(A, n))
CROSSREFS
KEYWORD
nonn
AUTHOR
Michael Somos, Mar 06 2004
STATUS
approved