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A200316 Number of permutations of [1..n] that can be drawn on a circle. 0
1, 2, 6, 22, 84, 308, 1090, 3782, 13000, 44504, 152102, 519506, 1773948, 6056932, 20680010, 70606382, 241065744, 823050480, 2810070734, 9594182314, 32756588164, 111837988444, 381838777906, 1303679135238, 4451038985688, 15196797672872, 51885112720758, 177146855537986 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..28.

Vincent Vatter and Steve Waton: On Points Drawn from a Circle, Electronic J. Combin., 18 (2011), # P223.

Index entries for linear recurrences with constant coefficients, signature (7,-17,19,-10,2).

FORMULA

Vatter and Waton give a g.f.

G.f.: x*(2*x^5-4*x^4+5*x^3-9*x^2+5*x-1) / ((x-1)^3*(2*x^2-4*x+1)). - Colin Barker, Jul 05 2013

MATHEMATICA

Rest[CoefficientList[Series[x (2x^5-4x^4+5x^3-9x^2+5x-1)/((x-1)^3 (2x^2- 4x+ 1)), {x, 0, 30}], x]] (* Harvey P. Dale, Sep 29 2013 *)

CROSSREFS

Sequence in context: A150241 A150242 A150243 * A164870 A121686 A245904

Adjacent sequences:  A200313 A200314 A200315 * A200317 A200318 A200319

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Nov 29 2011

STATUS

approved

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Last modified January 22 19:44 EST 2020. Contains 331153 sequences. (Running on oeis4.)