OFFSET
1,2
COMMENTS
Column 1 of A211963.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..74
FORMULA
Empirical: a(n) = (1/8)*n^4 + (1/4)*n^3 - (9/8)*n^2 + (7/4)*n for n>1.
Conjectures from Colin Barker, Jul 20 2018: (Start)
G.f.: x^2*(3 - 3*x + 7*x^2 - 5*x^3 + x^4) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>6.
(End)
EXAMPLE
Some solutions for n=4:
..0........0........0........0........0........0........0........0
..1.2......1.2......1.2......1.2......1.1......1.2......1.2......1.2
..3.4.5....3.0.4....3.4.5....3.4.5....2.3.4....1.3.4....3.4.0....3.4.5
..3.6.7.8..5.6.7.8..6.7.8.0..6.0.7.8..5.6.7.8..5.6.7.8..5.6.7.8..6.7.8.1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 26 2012
STATUS
approved