OFFSET
1,2
COMMENTS
Row 1 of A200430.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..200
FORMULA
Empirical: a(n) = (16/3)*n^3 - 6*n^2 + (2/3)*n.
Conjectures from Colin Barker, May 20 2018: (Start)
G.f.: 4*x^2*(5 + 3*x) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.
(End)
EXAMPLE
Some solutions for n=3:
.-3...-2....1....3...-3....2...-3...-1....2....1...-1...-1....1....3...-2...-1
.-1....1...-2...-2....2....3...-2....0...-1....0...-1...-1...-3...-2....1....2
..2....2....3....0....2...-2....3....3...-3....2....3...-1....1...-3...-2....0
..2...-1...-2...-1...-1...-3....2...-2....2...-3...-1....3....1....2....3...-1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 17 2011
STATUS
approved