A291887 Number of symmetrically unique Dyck paths of semilength n and height three.

1, 3, 11, 31, 91, 250, 690, 1863, 5017, 13389, 35621, 94354, 249352, 657421, 1730685, 4550031, 11950963, 31365810, 82274126, 215711947, 565376593, 1481448697, 3881041065, 10165822434, 26624745964, 69725071281, 182583838181, 478093234315, 1251829592839

Offset

3,2

Links

Alois P. Heinz, Table of n, a(n) for n = 3..1000

Index entries for linear recurrences with constant coefficients, signature (6, -9, -8, 27, -10, -10, 4).

Formula

G.f.: -x^3*(x^4+2*x^2-3*x+1)/((2*x-1)*(x^2-3*x+1)*(2*x^2-1)*(x^2+x-1)).

Crossrefs

Column k=3 of A291883.

Sequence in context: A320238 A369399 A108898 * A217323 A263781 A119901

Adjacent sequences: A291884 A291885 A291886 * A291888 A291889 A291890

Keyword

nonn,easy

Author

Alois P. Heinz, Sep 05 2017

Status

approved