OFFSET
0,3
COMMENTS
Related q-series identity:
Sum_{n>=1} z^n*y*q^n/(1-y*q^(2*n)) = Sum_{n>=1} y^n*z*q^(2*n-1)/(1-z*q^(2*n-1)); here q=x, y=1, z=A(x).
FORMULA
G.f. satisfies: A(x) = 1 + Sum_{n>=1} A(x)*x^(2*n-1)/(1 - A(x)*x^(2*n-1)).
EXAMPLE
G.f.: A(x) = 1 + x + 2*x^2 + 6*x^3 + 16*x^4 + 49*x^5 + 156*x^6 +...
which satisfies the following relations:
A(x) = 1 + A(x)*x/(1-x^2) + A(x)^2*x^2/(1-x^4) + A(x)^3*x^3/(1-x^6) +...
A(x) = 1 + A(x)*x/(1-A(x)*x) + A(x)*x^3/(1-A(x)*x^3) + A(x)*x^5/(1-A(x)*x^5) +...
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+sum(m=1, n, A^m*x^m/(1-x^(2*m)+x*O(x^n)))); polcoeff(A, n)}
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=1+sum(m=1, n, A*x^(2*m-1)/(1-A*x^(2*m-1)+x*O(x^n)))); polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jun 30 2011
STATUS
approved