A116769 Number of permutations of length n which avoid the patterns 1234, 4123, 4132.

1, 2, 6, 21, 76, 263, 843, 2501, 6941, 18245, 45928, 111721, 264482, 612707, 1394929, 3131269, 6948043, 15269985, 33290710, 72085673, 155182152, 332387343, 708820807, 1505731877, 3187639497, 6727621949, 14159916404, 29729158217

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 183.

Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.

Index entries for linear recurrences with constant coefficients, signature (10,-43,104,-155,146,-85,28,-4).

Formula

G.f.: A(x) = -{x(3x^7-20x^6+54x^5-71x^4+57x^3-29x^2+8x-1)}/{(2x-1)^2(x-1)^6}

Crossrefs

Sequence in context: A304781 A148490 A006612 * A294817 A294772 A294818

Adjacent sequences: A116766 A116767 A116768 * A116770 A116771 A116772

Keyword

nonn,easy

Author

Lara Pudwell, Feb 26 2006

Status

approved