OFFSET
1,3
COMMENTS
Row 4 of A187155.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..50
FORMULA
Empirical: a(n) = 36*n^2 - 168*n + 188 for n>2.
Conjectures from Colin Barker, Apr 20 2018: (Start)
G.f.: 4*x^3*(2 + 17*x - x^2) / (1 - x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>5.
(End)
EXAMPLE
Some solutions for 4 X 4:
..0..0..4..0....0..0..0..0....0..0..0..0....0..0..4..0....0..4..0..0
..0..3..0..1....0..0..2..0....0..0..4..0....0..3..0..0....3..0..1..0
..0..0..2..0....0..3..0..1....0..3..0..1....0..0..2..0....0..2..0..0
..0..0..0..0....4..0..0..0....0..0..2..0....0..0..0..1....0..0..0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 06 2011
STATUS
approved