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A293995 Number of linear chord diagrams having n chords and no chord length larger than three. 2
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 (list; graph; refs; listen; history; text; internal format)
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)).

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

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Last modified June 16 14:16 EDT 2021. Contains 345057 sequences. (Running on oeis4.)