OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 14*a(n-1) - 49*a(n-2) for n>4.
Conjectures from Colin Barker, Jan 21 2019: (Start)
G.f.: 4*x*(4 - 2*x - 29*x^2 + 9*x^3) / (1 - 7*x)^2.
a(n) = 36 * 7^(n-4) * (120*n+53) for n>2.
(End)
EXAMPLE
Some solutions for n=4:
..0..0..2..1. .1..0..1..3. .1..3..2..2. .2..0..2..2. .3..1..3..2
..2..2..3..3. .1..1..2..2. .3..2..2..0. .1..0..3..1. .0..3..2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 21 2016
STATUS
approved