A116839 Number of permutations of length n which avoid the patterns 1234, 1243, 3241.

1, 2, 6, 21, 73, 238, 724, 2078, 5706, 15161, 39319, 100168, 251846, 627046, 1549898, 3810125, 9328073, 22766362, 55432684, 134725294, 326982110, 792733065, 1920267887, 4648446316, 11246721414, 27199650590, 65759222454, 158940539445

Offset

1,2

Links

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

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 81.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (9,-31,47,-16,-38,37,5,-15,1,2).

Formula

G.f.: x*(2x^10 -x^9 -11x^8 +6x^7 +7x^6 -20x^5 +8x^4 +18x^3 -19x^2 +7x-1) /((2x-1) (x^2-1+x)^2 (x-1)^3 (x^2+2x-1)).

Crossrefs

Sequence in context: A294799 A294693 A116757 * A294800 A116776 A116754

Adjacent sequences: A116836 A116837 A116838 * A116840 A116841 A116842

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved