OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = (1/5040)*n^7 + (1/180)*n^6 + (1/18)*n^5 + (11/36)*n^4 + (877/720)*n^3 + (287/90)*n^2 + (439/84)*n + 4 for n>4.
Conjectures from Colin Barker, Sep 06 2018: (Start)
G.f.: x*(10 - 38*x + 64*x^2 - 31*x^3 - 67*x^4 + 148*x^5 - 137*x^6 + 56*x^7 + 12*x^8 - 26*x^9 + 12*x^10 - 2*x^11) / (1 - x)^8.
a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>12.
(End)
EXAMPLE
Some solutions for n=4:
..1..3....0..2....0..2....2..4....1..2....1..2....0..0....0..2....0..0....1..2
..2..3....2..2....1..2....2..2....3..4....2..2....1..2....1..2....1..2....2..2
..2..2....4..2....2..3....3..2....4..4....2..0....2..3....2..3....2..2....2..1
..2..2....4..2....2..4....4..4....4..4....3..2....2..2....2..2....3..2....2..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jun 25 2013
STATUS
approved