OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-1) + 50*a(n-2) - 26*a(n-3) - 253*a(n-4) + 240*a(n-5) + 416*a(n-6) - 624*a(n-7).
Empirical g.f.: 4*x*(3 + 12*x - 11*x^2 - 54*x^3 + 68*x^4 + 86*x^5 - 156*x^6) / (1 - 6*x - 50*x^2 + 26*x^3 + 253*x^4 - 240*x^5 - 416*x^6 + 624*x^7). - Colin Barker, Oct 25 2018
EXAMPLE
Some solutions for n=5:
..4..1....4..3....2..3....1..3....2..3....3..2....2..1....3..2....1..4....1..2
..1..0....1..0....3..0....3..0....3..1....1..0....1..3....1..4....4..3....4..1
..3..4....4..0....2..0....3..0....1..0....2..1....1..2....1..3....4..1....1..0
..2..3....2..4....1..2....4..0....2..1....2..1....2..0....4..1....3..1....3..1
..2..4....2..0....2..4....3..4....2..1....1..2....2..4....1..3....3..1....1..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 11 2014
STATUS
approved