OFFSET
0,1
COMMENTS
Conjecture: a(n) is the number of letters (0's and 1's) in the n-th iteration of the mapping 00->001, 1->011, starting with 00; see A286939.
LINKS
Index entries for linear recurrences with constant coefficients, signature (2, 1, -1).
FORMULA
a(n) = 2*a(n-1) + a(n-2) - a(n-3), where a(0) = 2, a(1) = 3, a(2) = 6.
G.f.: (2 - x - 2*x^2)/(1 - 2*x - x^2 + x^3).
MATHEMATICA
LinearRecurrence[{2, 1, -1}, {2, 3, 6}, 40]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 05 2017
STATUS
approved