OFFSET
1,1
COMMENTS
Column 2 of A222871.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 21*a(n-1) - 84*a(n-2) + 64*a(n-3) for n>5.
Empirical g.f.: x*(2 - 35*x + 55*x^2 + 116*x^3 - 48*x^4) / ((1 - x)*(1 - 4*x)*(1 - 16*x)). - Colin Barker, Aug 16 2018
EXAMPLE
Some solutions for n=3:
..0..0....0..1....0..0....0..0....0..1....0..1....0..1....0..1....0..1....0..1
..1..2....2..2....1..2....1..2....2..3....0..2....0..2....2..1....2..3....2..3
..1..3....1..3....3..4....1..2....1..0....3..4....3..3....3..3....4..5....4..4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 07 2013
STATUS
approved