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A132647 Number of permutations of [n] having no substring [k,k+1,k+2,k+3]. 1
1, 1, 2, 6, 23, 117, 706, 4962, 39817, 359171, 3597936, 39630372, 476066277, 6194080387, 86776390796, 1302376048620, 20847721870931, 354549730559949, 6384006047649910, 121330369923079290, 2427196999663678987, 50981866833670160201, 1121806937829102793662 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..200

D. M. Jackson and R. C. Read, A note on permutations without runs of given length, Aequationes Math. 17 (1978), no. 2-3, 336-343.

FORMULA

G.f.: Sum_{n>=0} n!*((x^m-x)/(x^m-1))^n where m = 4.

PROG

(PARI) seq(n)={Vec(sum(k=0, n, k!*((x^4-x)/(x^4-1) + O(x*x^n))^k))} \\ Andrew Howroyd, Aug 31 2018

CROSSREFS

Cf. A000255, A002628.

Sequence in context: A185334 A290280 A059513 * A177253 A020122 A327426

Adjacent sequences:  A132644 A132645 A132646 * A132648 A132649 A132650

KEYWORD

nonn

AUTHOR

Ivana Jovovic (ivana121(AT)EUnet.yu), Nov 14 2007

EXTENSIONS

Terms a(16) and beyond from Andrew Howroyd, Aug 31 2018

STATUS

approved

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Last modified November 22 00:32 EST 2019. Contains 329383 sequences. (Running on oeis4.)