OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (8/3)*n^3 - (45/2)*n^2 + (257/6)*n + 330 for n>13.
Conjectures from Colin Barker, Oct 26 2018: (Start)
G.f.: x*(7 - 9*x + 5*x^2 + 7*x^3 + 13*x^4 - 33*x^5 + 12*x^6 + 12*x^7 + 2*x^8 + 7*x^9 - 4*x^10 + 10*x^11 - 10*x^12 - 10*x^13 + 9*x^14 - 3*x^15 + x^16) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>17.
(End)
EXAMPLE
Some solutions for n=5:
..0..0..0..0..2..2....0..0..0..0..0..0....0..0..0..0..0..0....0..0..2..2..0..0
..0..0..0..2..2..1....0..0..0..0..0..0....0..0..0..0..0..2....0..0..2..1..2..2
..0..0..0..2..1..2....2..2..0..0..0..0....0..0..0..0..0..2....0..0..0..2..2..1
..0..0..0..0..2..2....2..1..2..2..0..0....2..2..0..0..0..0....0..0..0..2..1..2
..2..2..0..0..0..0....0..2..2..1..2..0....2..1..2..2..0..0....2..2..0..0..1..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 17 2014
STATUS
approved