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A293997 Number of linear chord diagrams having n chords and no chord length larger than five. 2
1, 1, 3, 15, 105, 945, 3465, 14857, 72905, 393565, 2152693, 10317169, 49808117, 247455873, 1256019673, 6371895677, 31696702545, 157383838325, 785587613797, 3938599251649, 19742522444733, 98655068282297, 492637126850897, 2462204077446773, 12316715419452585 (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 (3, 4, 2, 81, 495, -648, -1590, 208, -5670, -924, 14576, -1536, -2136, -9936, 10656, -2880)

FORMULA

G.f.: -(24*x^11-84*x^10+76*x^9+20*x^8-10*x^7-90*x^6+12*x^5+35*x^4+4*x^2+2*x-1) / ((5*x-1) *(576*x^15 -2016*x^14 +1584*x^13 +744*x^12 +456*x^11 -2824*x^10 -380*x^9 +1058*x^8 +170*x^7 +352*x^6 +200*x^5 -59*x^4 -28*x^3 -6*x^2 -2*x-1)).

CROSSREFS

Column k=5 of A293960.

Sequence in context: A251598 A338725 A295871 * A328866 A247304 A293998

Adjacent sequences:  A293994 A293995 A293996 * A293998 A293999 A294000

KEYWORD

nonn,easy

AUTHOR

Alois P. Heinz, Oct 21 2017

STATUS

approved

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Last modified June 20 15:21 EDT 2021. Contains 345165 sequences. (Running on oeis4.)