A116733 Number of permutations of length n which avoid the patterns 321, 1324, 2341.

1, 2, 5, 12, 24, 41, 63, 90, 122, 159, 201, 248, 300, 357, 419, 486, 558, 635, 717, 804, 896, 993, 1095, 1202, 1314, 1431, 1553, 1680, 1812, 1949, 2091, 2238, 2390, 2547, 2709, 2876, 3048, 3225, 3407, 3594, 3786, 3983, 4185, 4392, 4604, 4821, 5043, 5270

Offset

1,2

Links

Table of n, a(n) for n=1..48.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

Formula

G.f.: A(x) = -{x(x^4+2x^3+2x^2-x+1)}/{(x-1)^3}

For n >= 3, a(n) = (5n^2 - 21n + 28)/2. - Franklin T. Adams-Watters, Sep 16 2006

Crossrefs

Sequence in context: A326510 A112287 A127787 * A116721 A294868 A192981

Adjacent sequences: A116730 A116731 A116732 * A116734 A116735 A116736

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved