OFFSET
1,2
COMMENTS
Row 2 of A221828.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 5*a(n-1) - 2*a(n-2) for n>4.
Conjectures from Colin Barker, Aug 11 2018: (Start)
G.f.: x^2*(3 + x - x^2) / (1 - 5*x + 2*x^2).
a(n) = (2^(-4-n)*((5-sqrt(17))^n*(-7+sqrt(17)) + (5+sqrt(17))^n*(7+sqrt(17)))) / sqrt(17) for n>2.
(End)
EXAMPLE
Some solutions for n=3:
..1..1..0....0..2..0....0..2..1....0..2..1....1..1..1....0..2..2....1..1..0
..2..1..1....1..2..1....1..2..0....1..1..1....1..2..0....0..1..1....1..2..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 26 2013
STATUS
approved