OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = n^6 + 6*n^5 + 11*n^4 + 4*n^3 - n^2 + n.
Conjectures from Colin Barker, Jan 23 2019: (Start)
G.f.: 2*x*(11 + 154*x + 204*x^2 - 14*x^3 + 5*x^4) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(End)
EXAMPLE
Some solutions for n=3:
..1. .2. .1. .2. .1. .2. .1. .0. .1. .3. .1. .0. .3. .0. .3. .2
..0. .3. .0. .1. .0. .0. .0. .3. .3. .0. .1. .2. .0. .2. .2. .1
..3. .3. .1. .2. .2. .1. .0. .0. .3. .1. .3. .1. .1. .0. .0. .0
..0. .1. .3. .2. .1. .3. .2. .3. .0. .0. .2. .1. .1. .3. .1. .1
..2. .1. .2. .0. .3. .1. .0. .2. .0. .0. .2. .3. .0. .2. .0. .0
..2. .0. .1. .0. .1. .2. .2. .3. .2. .1. .3. .3. .1. .2. .0. .2
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 27 2016
STATUS
approved