OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 10*a(n-1) - 35*a(n-2) + 50*a(n-3) - 24*a(n-4); a(n) = (18104*4^n - 26144*3^n + 10680*2^n - 644)/12.
Empirical g.f.: x*(1225 - 4213*x + 7302*x^2 - 3992*x^3) / ((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)). -Colin Barker, Nov 21 2018
EXAMPLE
Some solutions for n=3:
..3..1..1..1....2..2..2..2....3..3..2..3....1..1..0..0....1..1..1..1
..1..1..1..1....1..2..2..3....2..2..2..3....0..0..0..0....1..1..3..3
..1..1..3..3....1..2..2..3....0..1..1..2....2..2..3..3....0..0..2..2
..1..1..3..3....0..1..2..3....0..1..1..3....2..2..3..3....0..1..3..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 28 2014
STATUS
approved