OFFSET
1,2
COMMENTS
Column 6 of A215788.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 16*a(n-2) - 3*a(n-4).
Empirical g.f.: x*(1 + 3*x)*(1 - x - x^2) / (1 - 16*x^2 + 3*x^4). - Colin Barker, Jul 23 2018
EXAMPLE
Some solutions for n=4:
..0..x..1..x..3..x....0..x..1..x..3..x....0..x..1..x..2..x....0..x..1..x..2..x
..x..2..x..5..x..8....x..2..x..5..x..7....x..3..x..4..x..6....x..3..x..4..x..5
..4..x..6..x..9..x....4..x..6..x..9..x....5..x..7..x..9..x....6..x..7..x..9..x
..x..7..x.10..x.11....x..8..x.10..x.11....x..8..x.10..x.11....x..8..x.10..x.11
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 23 2012
STATUS
approved