OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 3*a(n-2) + a(n-3).
Conjectures from Colin Barker, Sep 13 2018: (Start)
G.f.: 2*x / ((1 + x)*(1 - 2*x - x^2)).
a(n) = (-2*(-1)^n + (1-sqrt(2))^n + (1+sqrt(2))^n) / 2.
(End)
EXAMPLE
Some solutions for n=4:
..1..0..0..1....1..0..0..1....1..0..0..0....1..0..0..1....1..0..0..1
..0..0..0..0....0..0..1..0....0..0..0..1....1..0..1..0....0..0..0..1
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 04 2013
STATUS
approved