OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (34/3)*n^3 + 28*n^2 + (104/3)*n + 16.
Conjectures from Colin Barker, Nov 22 2018: (Start)
G.f.: 2*x*(45 - 36*x + 33*x^2 - 8*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=4:
..3..3..2..3..3....2..1..1..1..1....2..2..3..3..3....2..2..2..1..0
..0..0..1..2..2....0..1..1..1..3....1..1..2..2..3....1..1..1..2..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 28 2014
STATUS
approved