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->0101, 1->100, starting with 00; see A288426.
LINKS
Clark Kimberling, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (2, -1, 1, -1).
FORMULA
a(n) = 2*a(n-1) - a(n-2) + a(n-3) - a(n-4), where a(0) = 2, a(1) = 4, a(2) = 5. a(3) = 6.
G.f.: (2 - x^2 - 2*x^3)/(1 - 2*x + x^2 - x^3 + x^4).
a(n) = a(n-1) + a(n-3) - 1, for n > 2. - Greg Dresden, Feb 09 2020
MATHEMATICA
LinearRecurrence[{2, -1, 1, -1}, {2, 4, 5, 6}, 40]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 11 2017
STATUS
approved