OFFSET
1,1
COMMENTS
Column 2 of A208434.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
Index entries for linear recurrences with constant coefficients, signature (4).
FORMULA
Empirical: a(n) = 4*a(n-1) for n>3.
Conjectures from Colin Barker, Feb 23 2018: (Start)
G.f.: 2*x*(1 + 3*x - x^2) / (1 - 4*x).
a(n) = 27*2^(2*n - 5) for n>2.
(End)
EXAMPLE
Some solutions for n=4:
..0..0....0..0....0..0....0..1....0..0....0..0....0..1....0..0....0..0....0..0
..1..1....0..0....1..1....2..1....1..2....0..0....0..2....0..1....1..1....0..0
..1..1....1..2....1..2....2..1....1..2....1..2....2..2....2..1....2..1....1..1
..2..0....1..2....2..2....0..1....0..0....2..2....0..1....2..1....0..2....1..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 26 2012
STATUS
approved