OFFSET
1,2
COMMENTS
Column 5 of A181196.
LINKS
R. H. Hardin, Table of n, a(n) for n=1..100
FORMULA
Empirical: a(n) = 24*a(n-1) - 40*a(n-2) - 8*a(n-3).
Conjectures from Colin Barker, Feb 27 2018: (Start)
G.f.: x*(1 - 10*x - 6*x^2) / ((1 - 2*x)*(1 - 22*x - 4*x^2)).
a(n) = 2^(n-2) + ((11-5*sqrt(5))^n*(2+sqrt(5)) + (-2+sqrt(5))*(11+5*sqrt(5))^n) / (4*sqrt(5)).
(End)
EXAMPLE
Some solutions for 4 X 5:
..1..2..3..4..5....1..2..3..4..5....1..2..3..4..5....1..2..3..4..5
..6..7..8..9.10....6..7..8..9.10....6..7..8..9.10....6..7..8..9.10
.11.12.13.14.15...11.12.13.14.17...11.12.13.14.16...11.12.13.14.18
.16.17.18.19.20...15.16.18.19.20...15.17.18.19.20...15.16.17.19.20
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 10 2010
STATUS
approved