A293995 Number of linear chord diagrams having n chords and no chord length larger than three.

1, 1, 3, 15, 35, 103, 343, 979, 2915, 8935, 26559, 79499, 239547, 717455, 2151095, 6459027, 19371507, 58106071, 174349295, 523022555, 1569013931, 4707208351, 14121515303, 42364215075, 127093528675, 381280144743, 1143838446943, 3431519977579, 10294558387995

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (2,1,8,-6)

Formula

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

Mathematica

LinearRecurrence[{2, 1, 8, -6}, {1, 1, 3, 15}, 30] (* Harvey P. Dale, Aug 08 2021 *)

Crossrefs

Column k=3 of A293960.

Sequence in context: A338351 A145949 A015809 * A015715 A187787 A290717

Adjacent sequences: A293992 A293993 A293994 * A293996 A293997 A293998

Keyword

nonn,easy

Author

Alois P. Heinz, Oct 21 2017

Status

approved