OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/40320)*n^8 - (1/2016)*n^7 + (7/576)*n^6 - (23/360)*n^5 + (1327/5760)*n^4 + (1271/288)*n^3 - (25027/672)*n^2 + (127387/840)*n - 223 for n>4.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(4 - 21*x + 52*x^2 - 72*x^3 + 54*x^4 - 8*x^5 - 32*x^6 + 55*x^7 - 67*x^8 + 66*x^9 - 46*x^10 + 20*x^11 - 4*x^12) / (1 - x)^9.
a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>13.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..3....3..1....0..3....3..3....3..1....3..1....0..0....3..1....0..0
..0..3....0..3....0..2....0..3....0..0....0..2....0..2....0..3....0..2....0..0
..3..3....3..1....3..3....3..1....3..3....0..3....0..3....3..3....0..0....0..3
..0..2....0..2....3..2....3..2....3..2....3..3....0..3....0..3....0..3....0..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 04 2014
STATUS
approved