OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 13*a(n-1) - 49*a(n-2) - 5*a(n-3) + 292*a(n-4) - 70*a(n-5) - 658*a(n-6) - 344*a(n-7).
Empirical g.f.: x*(5 - 40*x + 40*x^2 + 262*x^3 - 199*x^4 - 748*x^5 - 362*x^6) / ((1 - 4*x)*(1 - 9*x + 13*x^2 + 57*x^3 - 64*x^4 - 186*x^5 - 86*x^6)). - Colin Barker, Jan 24 2019
EXAMPLE
Some solutions for n=7:
..0. .1. .1. .4. .3. .2. .1. .2. .1. .2. .4. .4. .1. .3. .4. .1
..1. .0. .4. .1. .1. .1. .4. .4. .1. .3. .2. .1. .4. .4. .1. .1
..4. .0. .4. .0. .0. .0. .1. .1. .2. .0. .2. .4. .0. .3. .0. .2
..4. .4. .2. .1. .0. .1. .1. .1. .3. .3. .4. .4. .1. .2. .4. .1
..0. .4. .4. .3. .2. .0. .3. .2. .2. .1. .2. .2. .1. .2. .2. .3
..1. .2. .3. .1. .3. .3. .4. .1. .0. .0. .4. .3. .2. .0. .1. .1
..3. .4. .1. .0. .1. .4. .4. .3. .4. .3. .0. .2. .4. .3. .0. .4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 01 2016
STATUS
approved