A293996 Number of linear chord diagrams having n chords and no chord length larger than four.

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

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: A359417 A359418 A354299 * A229726 A145624 A025547

Adjacent sequences: A293993 A293994 A293995 * A293997 A293998 A293999

Keyword

nonn,easy

Author

Alois P. Heinz, Oct 21 2017

Status

approved