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A116744
Number of permutations of length n which avoid the patterns 1243, 1432, 4213.
0
1, 2, 6, 21, 73, 242, 772, 2409, 7439, 22872, 70204, 215345, 660375, 2024866, 6208416, 19035179, 58361985, 178937794, 548622648, 1682074579, 5157232471, 15812048862, 48479661510, 148638395025, 455724560391, 1397249174878
OFFSET
1,2
LINKS
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 100 and 101.
FORMULA
G.f.: A(x) = -{(x^2-x+1)(2x^4-7x^3+10x^2-5x+1)x}/{(2x^4-7x^3+8x^2-5x+1)(x-1)^3}
MATHEMATICA
LinearRecurrence[{8, -26, 47, -52, 35, -13, 2}, {1, 2, 6, 21, 73, 242, 772}, 30] (* Harvey P. Dale, Sep 07 2019 *)
CROSSREFS
Sequence in context: A116822 A116797 A294804 * A165521 A294696 A116784
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved