OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 14*a(n-1) - 65*a(n-2) + 80*a(n-3) + 163*a(n-4) - 280*a(n-5) - 208*a(n-6).
Empirical g.f.: x*(5 - 45*x + 95*x^2 + 113*x^3 - 319*x^4 - 213*x^5) / ((1 - 4*x)^2*(1 - 6*x + x^2 + 24*x^3 + 13*x^4)). - Colin Barker, Jan 23 2019
EXAMPLE
Some solutions for n=7:
..1. .2. .1. .4. .4. .3. .3. .3. .0. .4. .4. .1. .4. .1. .4. .3
..3. .0. .1. .1. .0. .3. .2. .2. .4. .4. .3. .3. .0. .0. .3. .1
..1. .4. .0. .3. .3. .4. .3. .4. .1. .2. .1. .2. .0. .3. .1. .0
..3. .3. .4. .1. .4. .0. .2. .4. .4. .3. .4. .4. .4. .0. .0. .3
..1. .0. .2. .2. .2. .4. .3. .0. .0. .0. .1. .3. .0. .2. .4. .0
..2. .0. .0. .1. .4. .3. .1. .3. .0. .4. .3. .0. .4. .3. .0. .1
..3. .4. .0. .0. .2. .4. .0. .1. .4. .1. .1. .3. .1. .1. .4. .4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 29 2016
STATUS
approved