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

Author

Alois P. Heinz, Oct 21 2017

Keywords

• nonn
• easy

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)

Crossrefs

Column k=3 of A293960.

Programs

Mathematica

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

Formula

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