OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 12*a(n-3) + 16*a(n-5).
Empirical g.f.: x*(1 + 3*x + 9*x^2 + 4*x^3 + 12*x^4) / ((1 + 2*x + 4*x^2)*(1 - 3*x + 2*x^2 - 4*x^3)). - Colin Barker, Jan 08 2019
EXAMPLE
Some solutions for n=4:
..5.13.14..2..9....5.13.14..2..9....5..6.14..2..3...12.13..1..2..3
..0..1..6..3..4....0..1.12..3..4....0..1.19..7..4....0.18.19..7..4
.15.16..7..8.19...15..6..7..8.19...15.16.17..8..9....5..6.11..8..9
.10.11.12.17.18...10.11.16.17.18...10.11.12.13.18...10.15.16.17.14
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 17 2015
STATUS
approved