OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + 4*a(n-3) + a(n-4).
Empirical g.f.: x*(1 + x + 5*x^2 + x^3) / ((1 + x^2)*(1 - 4*x - x^2)). - Colin Barker, Jan 03 2019
EXAMPLE
Some solutions for n=4:
..7..1..2..3..4....0.13..9..3..4....0..8..9..3..4....7..1..9..3..4
.12..6..0..8..9...12..6..7..8..2...12..6.14..1..2...12.13..0..8..2
.10.11..5.13.14...10.11..5..1.14...10.11..5.13..7...10.11..5..6.14
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 01 2015
STATUS
approved