OFFSET
1,1
COMMENTS
Column 3 of A183904.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..62
FORMULA
Empirical: a(n) = (1/6)*n^3 + (5/2)*n^2 + (25/3)*n - 14 for n>1.
Conjectures from Colin Barker, Apr 05 2018: (Start)
G.f.: x*(5 - 6*x + 12*x^2 - 18*x^3 + 8*x^4) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>5.
(End)
EXAMPLE
All solutions for n=2:
..0....2....0....1....0....0....1....1....0....0....0....1....0....0
..2....2....0....3....1....0....1....1....0....0....1....1....1....0
..2....2....2....3....1....0....3....1....2....0....2....1....1....1
..3....2....3....3....2....0....3....3....2....2....3....1....2....1
..3....2....3....3....3....0....3....3....2....2....3....3....2....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 07 2011
STATUS
approved