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
Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
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
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved