OFFSET
1,1
COMMENTS
Column 2 of A219471.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/20160)*n^8 + (1/1260)*n^7 + (1/480)*n^6 + (4/45)*n^5 - (11/960)*n^4 + (277/180)*n^3 + (7607/5040)*n^2 + (61/70)*n.
Conjectures from Colin Barker, Jul 26 2018: (Start)
G.f.: x*(4 - 13*x + 19*x^2 - 7*x^3 - 8*x^4 + 10*x^5 - 2*x^6 - x^7) / (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>9.
(End)
EXAMPLE
Some solutions for n=3:
..2..2....0..0....1..1....1..1....2..2....1..1....1..1....0..0....1..1....1..1
..0..0....1..1....0..0....1..1....0..0....1..1....1..1....0..1....1..1....2..2
..0..1....3..3....0..3....0..0....0..3....1..3....1..2....0..0....3..3....2..3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 20 2012
STATUS
approved