OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
W. Kuszmaul, Fast Algorithms for Finding Pattern Avoiders and Counting Pattern Occurrences in Permutations, arXiv preprint arXiv:1509.08216, 2015
FORMULA
Empirical: a(n) = (1/24)*n^4 + (1/12)*n^3 + (11/24)*n^2 + (53/12)*n - 6 for n>2.
Conjectures from Colin Barker, Oct 26 2018: (Start)
G.f.: x*(1 - x + x^2)*(3 - 4*x + 4*x^3 - 2*x^4) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>7.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....3..3....0..3....0..0....0..3....0..0....0..0....0..0....0..0....0..3
..0..0....3..2....3..3....0..0....0..3....0..0....0..3....3..3....0..0....3..3
..0..3....0..0....3..2....0..0....3..1....0..3....3..3....3..3....0..3....3..2
..3..1....0..3....0..3....0..0....3..3....3..3....3..2....0..2....0..3....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 28 2014
STATUS
approved