OFFSET
1,1
COMMENTS
Row 1 of A255622.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/40320)*n^8 + (11/10080)*n^7 + (7/576)*n^6 + (7/180)*n^5 + (847/5760)*n^4 + (1007/1440)*n^3 + (1237/672)*n^2 + (913/280)*n + 3.
Empirical g.f.: x*(9 - 54*x + 162*x^2 - 276*x^3 + 300*x^4 - 216*x^5 + 99*x^6 - 26*x^7 + 3*x^8) / (1 - x)^9. - Colin Barker, Jan 21 2018
EXAMPLE
Some solutions for n=4:
..0....1....2....1....2....2....2....0....2....1....2....0....1....2....1....0
..0....0....0....1....0....0....0....1....0....2....2....0....1....1....2....0
..1....1....0....2....2....0....1....0....0....0....0....2....1....0....0....0
..2....1....1....0....0....1....0....0....1....2....2....2....1....0....1....2
..1....0....2....1....2....1....1....0....0....1....0....1....0....1....0....2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 28 2015
STATUS
approved