OFFSET
1,1
COMMENTS
Column 1 of A223449.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 6*a(n-2) - 4*a(n-4).
Empirical g.f.: x*(3 + 2*x)*(5 + 6*x - 12*x^2) / (1 - 6*x^2 + 4*x^4). - Colin Barker, Aug 20 2018
EXAMPLE
Some solutions for n=3:
.12...13....3....7....1....8....2....2....9....2....6....1....0....2...11....0
..9...10....1....4....0....4....0....9....2....0....3....0....2....9....9....2
..2...13....0....8....2....8....1...12...10....2....1....1....9...11....2....0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 20 2013
STATUS
approved