OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Myrto Kallipoliti, Robin Sulzgruber, and Eleni Tzanaki, Patterns in Shi tableaux and Dyck paths, arXiv:2006.06949 [math.CO], 2020.
Lara Pudwell, Systematic Studies in Pattern Avoidance, 2005.
Index entries for linear recurrences with constant coefficients, signature (7,-19,26,-19,7,-1)
FORMULA
G.f.: x*(1 - 5*x + 10*x^2 - 9*x^3 + 5*x^4 - x^5) / ((1 - x)^4*(1 - 3*x + x^2)).
a(n) = 1 - ((3-sqrt(5))/2)^n/sqrt(5) + ((3+sqrt(5))/2)^n/sqrt(5) - (4*n)/3 + n^2/2 - n^3/6. - Colin Barker, Oct 31 2017
PROG
(PARI) Vec(x*(1 - 5*x + 10*x^2 - 9*x^3 + 5*x^4 - x^5) / ((1 - x)^4*(1 - 3*x + x^2)) + O(x^40)) \\ Colin Barker, Oct 31 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lara Pudwell, Feb 26 2006
STATUS
approved