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 + (17/360)*n^5 + (6367/5760)*n^4 - (935/288)*n^3 + (28145/672)*n^2 - (114913/840)*n + 237 for n>6.
Conjectures from Colin Barker, Oct 27 2018: (Start)
G.f.: x*(12 - 47*x + 73*x^2 + 4*x^3 - 244*x^4 + 558*x^5 - 737*x^6 + 651*x^7 - 375*x^8 + 86*x^9 + 91*x^10 - 128*x^11 + 80*x^12 - 27*x^13 + 4*x^14) / (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>15.
(End)
EXAMPLE
Some solutions for n=5:
..0..3..3..0..0....0..3..3..0..0....0..0..0..0..3....0..3..3..0..0
..0..3..3..1..3....0..0..3..1..3....0..3..3..0..0....0..3..2..3..3
..0..3..3..2..0....0..0..2..1..2....0..0..2..1..3....0..3..1..0..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 30 2014
STATUS
approved