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->10, starting with 00; see A288462.
LINKS
Clark Kimberling, Table of n, a(n) for n = 0..2000
Index entries for linear recurrences with constant coefficients, signature (2, 0, 0, -1).
FORMULA
a(n) = 2*a(n-1) - a(n-4), where a(0) = 2, a(1) = 4, a(2) = 6. a(3) = 10.
G.f.: -((2*(-1 + x^2 + x^3))/(1 - 2*x + x^4)).
MATHEMATICA
LinearRecurrence[{2, 0, 0, -1}, {2, 4, 6, 10}, 40]
CoefficientList[Series[-((2(-1+x^2+x^3))/(1-2x+x^4)), {x, 0, 40}], x] (* Harvey P. Dale, Oct 14 2021 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jun 11 2017
STATUS
approved