A116822 Number of permutations of length n which avoid the patterns 2341, 3421, 4123.

1, 2, 6, 21, 73, 241, 766, 2399, 7514, 23648, 74706, 236352, 747770, 2364773, 7475960, 23631523, 74699975, 236139689, 746503680, 2359936092, 7460507061, 23584937695, 74558966315, 235702724400, 745125438325, 2355561039070

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 [math.CO] (2017), Table 2 No 97.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (8,-26,47,-51,35,-18,4,-1).

Formula

G.f.: A(x) = -{x(x^7-3x^6+12x^5-18x^4+22x^3-16x^2+6x-1)}/{x^8-4x^7+18x^6-35x^5+51x^4-47x^3+26x^2-8x+1}

Crossrefs

Sequence in context: A116773 A116741 A116843 * A116797 A294804 A116744

Adjacent sequences: A116819 A116820 A116821 * A116823 A116824 A116825

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved