OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + 5*a(n-2) + 7*a(n-3) + 4*a(n-4).
Empirical g.f.: x*(5 + 7*x + 8*x^2 + 4*x^3) / (1 - 4*x - 5*x^2 - 7*x^3 - 4*x^4). - Colin Barker, Dec 20 2018
EXAMPLE
Some solutions for n=4:
..4....6....4....8....3....6....6....6....2....2....2....3....4....4....3....3
..8....8....6....8....5....2....8....3....2....1....7....3....8....2....7....5
..4....1....5....6....8....4....2....1....4....7....6....8....6....6....5....8
..6....1....7....5....2....3....4....4....6....4....1....1....3....3....1....4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 15 2015
STATUS
approved