OFFSET
1,1
COMMENTS
Row 4 of A205341.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (4/3)*n^3 - (1/2)*n^2 + (7/6)*n.
Conjectures from Colin Barker, Jun 11 2018: (Start)
G.f.: x*(2 + 3*x + 3*x^2) / (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=5:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..2....5....3....2....2....1....5....2....5....4....1....5....4....4....5....2
..0....8....6....4....6....6....1....7....1....9....6....7....5....2....8....5
..3....3....5....1....5....2....2....3....5....4....5....4....2....4....5....4
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 26 2012
STATUS
approved