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 (11,-50,120,-160,112,-32).
FORMULA
G.f.: x*(1 - 9*x + 34*x^2 - 64*x^3 + 64*x^4 - 28*x^5 + 4*x^6) / ((1 - x)*(1 - 2*x)^5)
From Colin Barker, Oct 20 2017: (Start)
a(n) = (24*(-32+39*2^n) - 263*2^(1+n)*n + 165*2^n*n^2 - 13*2^(1+n)*n^3 + 3*2^n*n^4) / 384 for n>1.
a(n) = 11*a(n-1) - 50*a(n-2) + 120*a(n-3) - 160*a(n-4) + 112*a(n-5) - 32*a(n-6) for n>7.
(End)
PROG
(PARI) Vec(x*(1 - 9*x + 34*x^2 - 64*x^3 + 64*x^4 - 28*x^5 + 4*x^6) / ((1 - x)*(1 - 2*x)^5) + O(x^30)) \\ Colin Barker, Oct 20 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved