OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 6*a(n-3) + 4*a(n-4).
Empirical g.f.: x*(1 + 3*x + 18*x^2 + 6*x^3) / ((1 + 2*x^2)*(1 - 3*x - 2*x^2)). - Colin Barker, Jan 07 2019
EXAMPLE
Some solutions for n=4:
..0..8..2..1..4....0..8..9..3..4....0..8..2..3..4....7..1..0..3..2
..5..6.14..3..7...12..1..2..6..7....5..1..7..6..9....5..6.14..8..4
.10.11.12.13..9....5.11.10.13.14...10.11.12.13.14...10.11.12.13..9
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 12 2015
STATUS
approved