OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 16*a(n-1) - 93*a(n-2) + 220*a(n-3) - 115*a(n-4) - 168*a(n-5) - 44*a(n-6) - 16*a(n-7).
Empirical g.f.: x*(5 - 55*x + 190*x^2 - 163*x^3 - 136*x^4 - 40*x^5 - 12*x^6) / ((1 - 4*x)*(1 - 12*x + 45*x^2 - 40*x^3 - 45*x^4 - 12*x^5 - 4*x^6)). - Colin Barker, Jan 25 2019
EXAMPLE
Some solutions for n=7:
..3. .1. .0. .1. .4. .3. .4. .1. .1. .1. .1. .0. .2. .3. .2. .3
..2. .4. .3. .1. .1. .3. .3. .0. .2. .2. .2. .1. .2. .0. .0. .4
..0. .2. .1. .3. .2. .3. .2. .4. .0. .1. .3. .2. .3. .3. .2. .1
..4. .4. .1. .4. .2. .4. .1. .4. .2. .2. .0. .1. .0. .3. .3. .0
..0. .0. .1. .1. .2. .3. .1. .2. .1. .2. .4. .4. .1. .4. .0. .2
..2. .1. .3. .3. .3. .2. .4. .1. .0. .0. .1. .1. .0. .2. .3. .1
..2. .0. .4. .1. .0. .4. .2. .0. .1. .4. .2. .3. .1. .2. .3. .2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 01 2016
STATUS
approved