OFFSET
1,1
COMMENTS
Row 2 of A255622.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/40320)*n^8 + (13/10080)*n^7 + (59/2880)*n^6 + (61/360)*n^5 + (5167/5760)*n^4 + (901/1440)*n^3 + (17077/3360)*n^2 + (3977/280)*n + 6.
Empirical g.f.: x*(3 - 2*x)*(9 - 48*x + 130*x^2 - 195*x^3 + 171*x^4 - 87*x^5 + 24*x^6 - 3*x^7) / (1 - x)^9. - Colin Barker, Jan 21 2018
EXAMPLE
Some solutions for n=4:
..0....0....2....2....0....2....1....0....2....2....2....0....0....1....1....0
..0....2....0....0....2....0....1....2....0....1....1....1....0....1....2....1
..1....2....2....2....1....2....2....1....0....0....0....2....1....2....0....0
..1....1....1....2....2....2....2....0....2....0....0....0....2....1....2....2
..2....0....1....0....2....2....2....0....1....1....2....0....1....2....2....2
..2....1....2....2....2....1....0....0....2....0....1....2....1....0....0....1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 28 2015
STATUS
approved