

A107902


Expansion coefficients of the solution of a functional equation.


2



1, 2, 2, 2, 4, 12, 32, 72, 148, 318, 772, 2014, 5216, 13060, 32168, 80176, 204714, 531054, 1380492, 3574768, 9247262, 24023702, 62819630, 165074070, 434726670, 1145890266, 3024348486, 7999762500, 21214170582, 56378759128, 150069876570
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..31.


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(n1), sqrtint(n+2), x^((i^2+i)/2) * A^((i^2i)/2))); polcoeff(A, n))};


CROSSREFS

Sequence in context: A130707 A131562 A260786 * A142974 A259856 A279805
Adjacent sequences: A107899 A107900 A107901 * A107903 A107904 A107905


KEYWORD

nonn


AUTHOR

Michael Somos, May 26 2005


STATUS

approved



