OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/40)*n^5 + (1/3)*n^4 - (1/8)*n^3 + (5/3)*n^2 + (141/10)*n - 15 for n>2.
Conjectures from Colin Barker, Sep 06 2018: (Start)
G.f.: x*(7 - 16*x + 21*x^2 - 11*x^3 + 7*x^4 - 6*x^5 + x^7) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..0....0..1....1..2....0..1....0..0....0..1....0..0....0..0....1..1
..0..1....0..1....0..0....2..2....0..0....0..0....1..0....0..2....1..1....1..1
..2..1....0..0....0..0....2..2....1..0....1..2....1..0....0..2....0..0....2..1
..2..2....1..1....1..0....2..2....0..0....2..2....2..0....0..2....0..0....2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jun 27 2013
STATUS
approved