A206736 Number of permutations of length n which avoid the patterns 1234, 4321.

1, 1, 2, 6, 22, 86, 306, 882, 1764, 1764, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

0,3

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=0..113.

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

Formula

G.f.: 1764*x^9 + 1764*x^8 + 882*x^7 + 306*x^6 + 86*x^5 + 22*x^4 + 6*x^3 + 2*x^2 + x + 1.

a(n) = 0 for n >= 10.

Crossrefs

Begins in the same way as A079105.

Sequence in context: A150253 A150254 A148497 * A079105 A079104 A116705

Adjacent sequences: A206733 A206734 A206735 * A206737 A206738 A206739

Keyword

nonn,easy

Author

N. J. A. Sloane, Feb 11 2012

Extensions

a(0)=1 prepended by Alois P. Heinz, Nov 08 2025

Status

approved