A118410 G.f. A(x) = Sum_{n>=0} a(n)*x^n/2^(n*(n-1)/2) satisfies: A(x) = Sum_{n>=0} A(x)^n*x^n/2^(n*(n-1)/2).

1, 1, 3, 21, 321, 10385, 699073, 96908737, 27478721537, 15863659383041, 18583701166494721, 44066148876930001921, 211105432749968736673793, 2040201553888722742048509953, 39729701298130761785818052935681

Offset

0,3

Links

Table of n, a(n) for n=0..14.

Formula

G.f.: A(x) = (1/x)*series_reversion[x/Sum_{n>=0} x^n/2^(n*(n-1)/2)].

Example

A(x) = 1 + x + 3*x^2/2 + 21*x^3/8 + 321*x^4/64 + 10385*x^5/1024 +...
A(x) = 1 + x*A(x) + x^2*A(x)^2/2 + x^3*A(x)^3/8 +...

Prog

(PARI) {a(n)=2^(n*(n-1)/2)*polcoeff(1/x*serreverse(x/sum(k=0, n, x^k/2^(k*(k-1)/2)+x*O(x^n))), n)}

Crossrefs

Cf. A117401.

Sequence in context: A341471 A134528 A332974 * A125054 A113085 A240936

Adjacent sequences: A118407 A118408 A118409 * A118411 A118412 A118413

Keyword

nonn

Author

Paul D. Hanna, Apr 27 2006

Status

approved