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A116705 Number of permutations of length n which avoid the patterns 1234, 4312. 0
1, 2, 6, 22, 86, 321, 1085, 3266, 8797, 21478, 48206, 100728, 198046, 369617, 659505, 1131656, 1876481, 3018946, 4728382, 7230242, 10820046, 15879769, 22896941, 32486742, 45417389, 62639126, 85317142, 114868756, 153005222, 201778521 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Kremer, Darla; and Shiu, Wai Chee; Finite transition matrices for permutations avoiding pairs of length four patterns. Discrete Math. 268 (2003), no. 1-3, 171-183. MR1983276 (2004b:05006). See Table 1.

LINKS

Table of n, a(n) for n=1..30.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Wikipedia, Permutation classes avoiding two patterns of length 4

Index entries for linear recurrences with constant coefficients, signature (9,-36,84,-126,126,-84,36,-9,1).

FORMULA

G.f.: x*(4*x^8-19*x^7+32*x^6-39*x^5+62*x^4-44*x^3+24*x^2-7*x+1)/(1-x)^9

a(n) = (21*n^8 - 48*n^7 - 966*n^6 + 7728*n^5 - 8211*n^4 - 72912*n^3 + 311556*n^2 - 418608*n + 241920)/60480. - Franklin T. Adams-Watters, Sep 16 2006

CROSSREFS

Sequence in context: A206736 A079105 A079104 * A116708 A116706 A165524

Adjacent sequences:  A116702 A116703 A116704 * A116706 A116707 A116708

KEYWORD

nonn,easy

AUTHOR

Lara Pudwell, Feb 26 2006

STATUS

approved

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Last modified August 12 15:22 EDT 2022. Contains 356077 sequences. (Running on oeis4.)