OFFSET
1,2
COMMENTS
Column 7 of A215788.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 61*a(n-2) - 99*a(n-4) - 2*a(n-6).
Empirical g.f.: x*(1 + 5*x - 19*x^2 - 43*x^3 + 2*x^4 - 2*x^5) / (1 - 61*x^2 + 99*x^4 + 2*x^6). - Colin Barker, Jul 23 2018
EXAMPLE
Some solutions for n=4:
..0..x..1..x..2..x..3....0..x..1..x..3..x..4....0..x..1..x..2..x..6
..x..4..x..6..x..7..x....x..2..x..5..x..6..x....x..3..x..4..x..8..x
..5..x..8..x..9..x.12....7..x..8..x..9..x.10....5..x..7..x.10..x.12
..x.10..x.11..x.13..x....x.11..x.12..x.13..x....x..9..x.11..x.13..x
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 23 2012
STATUS
approved