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A293996 Number of linear chord diagrams having n chords and no chord length larger than four. 2
1, 1, 3, 15, 105, 315, 1141, 4779, 21101, 80559, 314185, 1267551, 5160933, 20504123, 81554685, 326682775, 1310978305, 5239019143, 20931551661, 83743554723, 335175239813, 1340542340399, 5360923216953, 21444223178271, 85786427569333, 343141430067947 (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 (2,2,11,60,-18,-26,-108,-48)

FORMULA

G.f.: -(2*x^4+4*x^3+x^2+x-1) / ((4*x-1) * (12*x^7+30*x^6+14*x^5+8*x^4-13*x^3 -6*x^2 -2*x-1)).

CROSSREFS

Column k=4 of A293960.

Sequence in context: A273197 A255427 A181131 * A229726 A145624 A025547

Adjacent sequences:  A293993 A293994 A293995 * A293997 A293998 A293999

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.)