OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Darla Kremer and Wai Chee Shiu, Finite transition matrices for permutations avoiding pairs of length four patterns, Discrete Math. 268 (2003), 171-183. MR1983276 (2004b:05006). See Table 1.
Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
Index entries for linear recurrences with constant coefficients, signature (8,-22,25,-10,2).
FORMULA
G.f.: -x*(2*x^4-7*x^3+12*x^2-6*x+1) / (2*x^5-10*x^4+25*x^3-22*x^2+8*x-1).
a(n) = 8*a(n-1) - 22*a(n-2) + 25*a(n-3) - 10*a(n-4) + 2*a(n-5) for n>5. - Colin Barker, Oct 20 2017
PROG
(PARI) Vec(x*(1 - 6*x + 12*x^2 - 7*x^3 + 2*x^4) / (1 - 8*x + 22*x^2 - 25*x^3 + 10*x^4 - 2*x^5) + O(x^30)) \\ Colin Barker, Oct 20 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved