OFFSET
1,2
FORMULA
G.f. A(x) satisfies A(x) = x * f(x, A(x)) where f(, ) is Ramanujan's general theta function.
EXAMPLE
G.f. = x + 2*x^2 + 2*x^3 + 2*x^4 + 4*x^5 + 12*x^6 + 32*x^7 + 72*x^8 + ...
PROG
(PARI) {a(n) = my(A); if( n<1, 0, A = x + O(x^2); for(k=2, n, A = x * sum(i= -sqrtint(n-1), sqrtint(n+2), x^((i^2+i)/2) * A^((i^2-i)/2))); polcoeff(A, n))};
CROSSREFS
KEYWORD
nonn
AUTHOR
Michael Somos, May 26 2005
STATUS
approved