OFFSET
1,1
COMMENTS
Column 2 of A220204.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/20160)*n^8 - (1/5040)*n^7 - (1/480)*n^6 + (107/720)*n^5 - (1151/960)*n^4 + (278/45)*n^3 - (54427/5040)*n^2 + (5323/420)*n - 7 for n>1.
Conjectures from Colin Barker, Jul 30 2018: (Start)
G.f.: x*(4 - 26*x + 92*x^2 - 215*x^3 + 350*x^4 - 386*x^5 + 277*x^6 - 119*x^7 + 29*x^8 - 4*x^9) / (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>10.
(End)
EXAMPLE
Some solutions for n=3:
..0..0....0..0....2..2....2..2....3..3....0..0....0..0....0..0....0..0....0..0
..0..0....0..0....3..2....0..0....3..3....0..0....0..0....0..0....3..0....1..0
..2..0....1..1....3..3....0..0....3..3....3..3....3..1....3..2....3..3....2..2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 07 2012
STATUS
approved