A367667 G.f. A(x) satisfies A(x) = 1 / (1 - x - x^3 * A(x^3)).

1, 1, 1, 2, 3, 4, 7, 11, 16, 26, 41, 62, 99, 156, 240, 379, 596, 925, 1453, 2281, 3556, 5575, 8742, 13658, 21394, 33524, 52432, 82100, 128597, 201233, 315058, 493377, 772247, 1209008, 1893055, 2963414, 4639389, 7263831, 11371536, 17802783, 27872601, 43635714

Offset

0,4

Links

Table of n, a(n) for n=0..41.

Formula

a(0) = 1; a(n) = a(n-1) + Sum_{k=0..floor((n-3)/3)} a(k) * a(n-3-3*k).

Prog

(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=v[i]+sum(j=0, (i-3)\3, v[j+1]*v[i-2-3*j])); v;

Crossrefs

Cf. A367659, A367666.

Cf. A218032.

Sequence in context: A023361 A210518 A113435 * A222022 A025048 A017987

Adjacent sequences: A367664 A367665 A367666 * A367668 A367669 A367670

Keyword

nonn

Author

Seiichi Manyama, Nov 26 2023

Status

approved