A116830 Number of permutations of length n which avoid the patterns 1324, 2431, 4123.

1, 2, 6, 21, 72, 229, 686, 1972, 5514, 15131, 40986, 110013, 293376, 778678, 2059646, 5434009, 14309508, 37628165, 98841306, 259426800, 680498610, 1784183887, 4676276006, 12253079101, 32099813532, 84080037314, 220207603686

Offset

1,2

Links

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

D. Callan, T. Mansour, Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns, arXiv:1705.00933 (2017), Table 2 No 46.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (7,-17,15,1,-7,2)

Formula

G.f.: A(x) = {(2x^6+3x^5+4x^4+2x^3-9x^2+5x-1)x}/{(x-1)(x^2-3x+1)(x^2-1+x)(2x-1)}

a(n) = 7*a(n-1) - 17*a(n-2) + 15*a(n-3) + a(n-4) - 7*a(n-5) + 2*a(n-6). - Wesley Ivan Hurt, Apr 18 2023

Crossrefs

Sequence in context: A116786 A116748 A116812 * A116747 A116810 A294703

Adjacent sequences: A116827 A116828 A116829 * A116831 A116832 A116833

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved