A196192 G.f. satisfies A(x) = 1/Product_{n>=1} (1 - x^n*A(x^n)^2).

1, 1, 4, 16, 77, 389, 2128, 12019, 70185, 418788, 2544938, 15687842, 97871618, 616729500, 3919686231, 25096525793, 161723865118, 1048085548563, 6826585371618, 44664343473618, 293407529533947, 1934484748893113, 12796683165889635, 84906535878961845

Offset: 0

Author

Paul D. Hanna, Sep 28 2011

Keywords

• nonn

Examples

			G.f.: A(x) = 1 + x + 4*x^2 + 16*x^3 + 77*x^4 + 389*x^5 + 2128*x^6 +...
where
A(x) = 1/((1 - x*A(x)^2) * (1 - x^2*A(x^2)^2) * (1 - x^3*A(x^3)^2) *...).
		

Crossrefs

Cf. A050383, A196191.

Programs

PARI

{a(n)=local(A=1+x); for(i=1, n, A=1/prod(k=1, n, (1-x^k*subst(A,x,x^k+x*O(x^n))^2))); polcoeff(A, n)}