OFFSET
0,1
COMMENTS
Empirically, a(n) is the number of letters (0's and 1's) in the n-th iterate of the mapping 00->1000, 10->010, starting with 00; see A288216.
LINKS
Clark Kimberling, Table of n, a(n) for n = 0..2000
Index entries for linear recurrences with constant coefficients, signature (1, 1).
FORMULA
a(n) = a(n-1) + a(n-2) for n >= 3, where a(0) = 2, a(1) = 4, a(2) = 7.
a(n) = L(n+2) for n >=1, where L = A000032 (Lucas numbers).
G.f.: (-2 - 2 x - x^2)/(-1 + x + x^2).
MATHEMATICA
Join[{2}, LinearRecurrence[{1, 1}, {4, 7}, 40]]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 19 2017
STATUS
approved