A116836 Number of permutations of length n which avoid the patterns 2341, 4132, 4321.

1, 2, 6, 21, 72, 233, 739, 2343, 7458, 23801, 76016, 242777, 775265, 2475513, 7904587, 25240597, 80598107, 257366469, 821825201, 2624260190, 8379812195, 26758495711, 85445488885, 272845382481, 871252605664, 2782092566535

Offset

1,2

Links

Table of n, a(n) for n=1..26.

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 54.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-19,29,-27,16,-10,7,-7,2).

Formula

G.f.: -(2x^8 -7x^7 +7x^6 -8x^5 +8x^4 -12x^3 +11x^2 -5x +1)*x/(2x^9 -7x^8 +7x^7 -10x^6 +16x^5 -27x^4 +29x^3 -19x^2 +7x-1).

Mathematica

LinearRecurrence[{7, -19, 29, -27, 16, -10, 7, -7, 2}, {1, 2, 6, 21, 72, 233, 739, 2343, 7458}, 30] (* Harvey P. Dale, May 04 2024 *)

Crossrefs

Sequence in context: A116800 A116758 A116838 * A116796 A116779 A116737

Adjacent sequences: A116833 A116834 A116835 * A116837 A116838 A116839

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved