A238426 Expansion of F(x) where F(x) = 1 + x / (1 - x * F(x) * F(-x^2) ).

1, 1, 1, 2, 3, 6, 13, 29, 65, 151, 359, 864, 2100, 5160, 12796, 31952, 80272, 202821, 515057, 1313716, 3364049, 8645559, 22291985, 57649712, 149496257, 388647248, 1012717568, 2644555020, 6919609962, 18139104129, 47632278280, 125282210973, 330016728365, 870564606345, 2299577632573, 6081963356452

Offset

0,4

Comments

What does this sequence count?

Links

Table of n, a(n) for n=0..35.

Prog

(PARI)
N=66;  R=O('x^N);  x='x+R;
F = 1;  for (k=1, N+1, F = 1 + x / (1 - x * F * subst(F, 'x, -'x^2) ) + R; );
Vec(F)

Crossrefs

Cf. A238427: F(x) = 1 + x / (1 - x * F(x) * F(+x^2) ).

Sequence in context: A287128 A286062 A219226 * A032066 A107316 A124682

Adjacent sequences: A238423 A238424 A238425 * A238427 A238428 A238429

Keyword

nonn

Author

Joerg Arndt, Feb 28 2014

Status

approved