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A116788
Number of permutations of length n which avoid the patterns 1234, 3142, 4132.
0
1, 2, 6, 21, 73, 240, 746, 2217, 6371, 17864, 49202, 133759, 360175, 963044, 2561604, 6787167, 17930815, 47267250, 124395032, 326966211, 858600521, 2253029402, 5908876016, 15490375561, 40595804773, 106364147270, 278630854386
OFFSET
1,2
FORMULA
G.f.: A(x) = -{(2x^5-9x^4+16x^3-15x^2+6x-1)x}/{(2x-1)(x-1)^3(x^2-3x+1)}
CROSSREFS
Sequence in context: A294694 A116740 A294802 * A294695 A116778 A116787
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved