OFFSET
1,1
COMMENTS
Row 4 of A211849.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (7/3)*n^3 + (27/2)*n^2 + (163/6)*n + 20.
Conjectures from Colin Barker, Jul 20 2018: (Start)
G.f.: x*(63 - 105*x + 76*x^2 - 20*x^3) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.
(End)
EXAMPLE
Some solutions for n=3:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....0....1....1....0....0....1....1....1....1....1....1....1....1....1
..1....1....0....1....1....1....1....1....1....1....1....1....1....1....0....0
..1....1....1....2....2....1....1....2....1....2....0....2....2....2....0....0
..2....2....1....2....2....0....2....2....2....2....0....2....2....2....0....0
..2....2....2....3....2....0....2....2....2....3....2....3....3....3....2....2
..2....3....2....3....3....2....3....3....3....2....0....3....3....3....2....2
..3....2....2....4....2....2....2....2....3....2....0....3....1....3....3....3
..2....2....3....4....2....3....2....2....4....4....3....0....1....4....3....3
..2....4....3....3....4....3....2....4....4....4....3....0....1....4....3....4
..4....4....4....3....2....4....4....4....2....0....4....4....4....5....4....4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 22 2012
STATUS
approved