OFFSET

1,1

COMMENTS

Column 2 of A219816.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = (1/12)*n^4 - (1/2)*n^3 + (41/12)*n^2 - 3*n + 1 for n>1.

Conjectures from Colin Barker, Jul 28 2018: (Start)

G.f.: x*(3 - 9*x + 16*x^2 - 17*x^3 + 11*x^4 - 2*x^5) / (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=3:

..1..1....0..0....0..0....0..0....0..0....1..1....2..2....0..0....1..1....0..0

..2..1....0..0....0..0....0..0....0..0....1..1....2..2....0..0....1..1....1..0

..2..2....2..0....1..0....0..0....1..1....2..1....2..2....2..1....2..2....2..2

CROSSREFS

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 28 2012

STATUS

approved