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A321311 Number of linear chord diagrams having n+2 chords and minimal chord length n. 0
10, 26, 79, 252, 796, 2468, 7564, 23012, 69676, 210308, 633484, 1905572, 5726956, 17201348, 51645004, 155016932, 465214636, 1395971588, 4188570124, 12567021092, 37703684716, 113116297028, 339359376844, 1018099102052, 3054339249196, 9163101633668, 27489472673164 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..27.

Index entries for linear recurrences with constant coefficients, signature (5, -6)

FORMULA

a(n) = A293881(n+2,n).

a(n) = 5*a(n-1) - 6*a(n-2) for n > 5.

a(n) = A293156(n) - 5*2^(n-1).

G.f.: x*(10 - 24*x + 9*x^2 + 13*x^3 + 10*x^4)/((1 - 2*x)*(1 - 3*x)). - Andrew Howroyd, Nov 17 2018

MATHEMATICA

Join[{10, 26, 79}, LinearRecurrence[{5, -6}, {252, 796}, 24]] (* Jean-Fran├žois Alcover, Nov 24 2018 *)

PROG

(PARI) Vec((10 - 24*x + 9*x^2 + 13*x^3 + 10*x^4)/((1 - 2*x)*(1 - 3*x)) + O(x^40)) \\ Andrew Howroyd, Nov 17 2018

CROSSREFS

A diagonal of A293881.

Cf. A257113, A293156.

Sequence in context: A005970 A192254 A220155 * A051966 A221568 A092774

Adjacent sequences:  A321308 A321309 A321310 * A321312 A321313 A321314

KEYWORD

nonn,easy

AUTHOR

Seiichi Manyama, Nov 17 2018

STATUS

approved

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Last modified April 3 14:34 EDT 2020. Contains 333197 sequences. (Running on oeis4.)