OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/360)*n^6 + (1/20)*n^5 + (5/18)*n^4 + (1/2)*n^3 + (439/360)*n^2 - (1/20)*n + 2.
Conjectures from Colin Barker, Dec 06 2018: (Start)
G.f.: x*(4 - 11*x + 28*x^2 - 37*x^3 + 27*x^4 - 11*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..0..1....0..0..0....0..1..1....0..0..1....0..1..2....0..1..2....0..1..1
..0..0..1....1..1..1....1..2..2....1..1..2....1..2..2....1..2..3....0..1..1
..1..1..2....1..1..2....2..2..3....1..2..2....2..3..3....1..2..3....1..1..2
..1..2..3....2..2..3....2..3..4....1..2..3....2..3..3....1..2..3....2..2..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 22 2014
STATUS
approved