OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/360)*n^6 + (1/120)*n^5 + (1/36)*n^4 + (5/24)*n^3 - (11/360)*n^2 + (167/60)*n + 2.
Conjectures from Colin Barker, Sep 17 2018: (Start)
G.f.: x*(5 - 25*x + 57*x^2 - 66*x^3 + 44*x^4 - 15*x^5 + 2*x^6) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(End)
EXAMPLE
Some solutions for n=4:
..0..2..2....0..2..2....0..2..2....0..2..2....0..2..2....0..2..2....0..2..2
..1..0..2....0..2..2....1..0..2....0..2..2....0..2..2....1..0..0....1..0..2
..1..0..2....1..0..2....1..0..2....1..0..2....0..2..2....1..1..1....1..1..0
..1..0..2....2..1..0....1..1..0....1..1..0....1..0..2....2..2..2....1..1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 23 2013
STATUS
approved