OFFSET
1,2
COMMENTS
Column 2 of A198982.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = 32*a(n-1) - 262*a(n-2) + 672*a(n-3) - 441*a(n-4).
Conjectures from Colin Barker, Feb 22 2018: (Start)
G.f.: x*(1 - 28*x + 168*x^2 - 231*x^3) / ((1 - x)*(1 - 3*x)*(1 - 7*x)*(1 - 21*x)).
a(n) = (189 + 56*3^n + 18*7^n + 21^n) / 504.
(End)
EXAMPLE
Some solutions with all values from 0 to 5 for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....2..3....2..3....2..3....2..3....2..3....2..3....2..0....2..0....2..0
..4..5....4..2....1..4....0..4....4..5....4..0....4..5....3..1....3..4....3..4
..2..0....0..5....0..5....2..5....1..2....0..5....0..4....4..5....5..2....0..5
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 01 2011
STATUS
approved