OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/6)*n^4 - (5/6)*n^3 + (13/3)*n^2 + (31/3)*n - 48 for n>5.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(2 + 2*x - 8*x^2 + 2*x^3 + 18*x^4 - 26*x^5 + 29*x^6 - 29*x^7 + 20*x^8 - 6*x^9) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>10.
(End)
EXAMPLE
Some solutions for n=4:
..3..0..0..0....3..0..0..0....3..0..0..0....3..0..0..0....3..0..0..0
..1..3..3..0....1..0..0..0....1..0..0..3....1..0..3..3....1..0..3..3
..3..1..3..2....3..0..2..3....3..0..0..1....3..2..3..2....3..0..2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 04 2014
STATUS
approved