A238427 Expansion of F(x) where F(x) = 1 + x / (1 - x * F(x) * F(+x^2) ).

1, 1, 1, 2, 5, 12, 31, 81, 219, 599, 1669, 4698, 13378, 38414, 111200, 324026, 949930, 2799477, 8289481, 24649698, 73580353, 220402603, 662285725, 1995853152, 6030654313, 18266757996, 55454844238, 168704450182, 514231352572, 1570282693387, 4803220361258, 14715518413613, 45150691283345, 138726758012623

Offset

0,4

Comments

What does this sequence count?

Links

Table of n, a(n) for n=0..33.

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. A238426: F(x) = 1 + x / (1 - x * F(x) * F(-x^2) ).

Sequence in context: A110035 A000635 A317098 * A077556 A076906 A097893

Adjacent sequences: A238424 A238425 A238426 * A238428 A238429 A238430

Keyword

nonn

Author

Joerg Arndt, Feb 28 2014

Status

approved