OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 30*a(n-1) - 261*a(n-2) + 540*a(n-3) - 324*a(n-4).
Empirical g.f.: 144*x*(1 - 7*x + 14*x^2 - 12*x^3) / (1 - 15*x + 18*x^2)^2. - Colin Barker, Jan 17 2019
EXAMPLE
Some solutions for n=3:
..0..1..2..0..1. .0..2..2..2..1. .1..0..1..0..0. .0..2..1..0..1
..2..2..1..0..0. .2..2..1..0..0. .1..0..0..1..0. .1..0..1..2..2
..1..0..0..1..2. .1..0..0..0..1. .2..1..0..1..0. .1..2..2..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 16 2016
STATUS
approved