OFFSET
1,2
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) + 8*a(n-4).
Empirical g.f.: x*(1 + 2*x^2 + 4*x^3) / (1 - 2*x - 8*x^4). - Colin Barker, Jan 08 2019
EXAMPLE
Some solutions for n=4:
..1..2..6..4..8....1..5..3..4..8....1..5..3..7..8....1..2..5..4..8
..0.10.11..3.13....0.10..2.12.13....0.10..2.12..4....0..7.10..3.12
..5.12..7.14..9...11..6..7.14..9...11..6.13.14..9...11..6.13.14..9
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 17 2015
STATUS
approved