OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 3*a(n-1) + 18*a(n-2) + 5*a(n-3) - 18*a(n-4) + 3*a(n-5) + a(n-6).
Empirical g.f.: x*(18 + 42*x - 7*x^2 - 33*x^3 + 7*x^4 + 2*x^5) / ((1 + x - x^2)*(1 - 4*x - 13*x^2 + 4*x^3 + x^4)). - Colin Barker, Jan 05 2019
EXAMPLE
Some solutions for n=4:
..2..4..0....0..1..5....2..1..0....3..1..2....0..1..2....0..1..2....0..4..2
..5..1..3....6..7..2....6..4..5....0..7..5....5..4..3....6..7..8....3..1..5
..8..7.11....3..4..8....3.10..8....8..4..6....6..7.11....3..4..5....8..7..6
..6.13.14....9.10.11...12..7..9...12.13..9....9.10..8....9.13.14...11.10..9
..9.10.12...12.13.14...14.13.11...14.10.11...12.13.14...12.10.11...12.13.14
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 08 2015
STATUS
approved