OFFSET
1,2
COMMENTS
Column 1 of A233113.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 9*a(n-1) - 23*a(n-2) + 15*a(n-3).
Conjectures from Colin Barker, Feb 19 2018: (Start)
G.f.: x*(1 - 7*x + 11*x^2) / ((1 - x)*(1 - 3*x)*(1 - 5*x)).
a(n) = (75 + 10*3^n + 3*5^n) / 120.
(End)
EXAMPLE
Some solutions for n=7:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....1....0....0....1....0....1....1....1....0....1....1....0....1....0....1
..2....2....0....1....5....1....5....2....1....1....5....5....1....0....1....2
..1....4....1....5....1....5....2....0....1....5....1....5....2....4....2....5
..5....0....1....1....1....4....0....3....5....5....1....1....1....2....1....5
..1....2....2....0....2....5....3....5....1....2....1....0....5....4....3....2
..5....2....0....1....5....4....1....2....0....5....5....0....2....2....3....5
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 04 2013
STATUS
approved