A026134 a(n) = Sum_{k=1..n} T(k, k-1), where T is the array in A026120.

1, 2, 6, 16, 44, 120, 329, 904, 2493, 6898, 19151, 53340, 149019, 417522, 1172979, 3303696, 9326931, 26390070, 74824584, 212565864, 604972998, 1724739940, 4925066567, 14085122376, 40339596755, 115688495806, 332203673142, 955090832416, 2749055259956, 7921280088744

Offset

1,2

Links

Table of n, a(n) for n=1..30.

Ricardo Gómez Aíza, Trees with flowers: A catalog of integer partition and integer composition trees with their asymptotic analysis, arXiv:2402.16111 [math.CO], 2024. See p. 21.

Formula

G.f.: z(1-z)M^3, with M the g.f. of the Motzkin numbers (A001006).

Crossrefs

T(n, n+2), where T is given by A026148, T(n, n-2), where T is the array defined in A026105 and T(n, n+1), where T is given by A026323.

First differences of A005322.

Cf. A026123.

Sequence in context: A118041 A105073 A002605 * A105696 A074413 A263897

Adjacent sequences: A026131 A026132 A026133 * A026135 A026136 A026137

Keyword

nonn

Author

Clark Kimberling

Extensions

a(25) corrected and more terms from Sean A. Irvine, Sep 17 2019

Status

approved