OFFSET
0,2
COMMENTS
For symmetry reasons, a(n) is a multiple of 4 for any n > 0.
LINKS
Rémy Sigrist, Table of n, a(n) for n = 0..999
Rémy Sigrist, Illustration of initial terms
Wikipedia, Golden square fractal
Index entries for linear recurrences with constant coefficients, signature (3,-2,0,2).
FORMULA
G.f.: (2*x^4 - 2*x^2 - x - 1)/(2*x^4 - 2*x^2 + 3*x - 1).
a(0) = 1.
a(n) = 3*a(n-1) - 2*a(n-2) + 2*a(n-4) for n > 4. - Stefano Spezia, Dec 02 2020
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Rémy Sigrist, Nov 24 2020
STATUS
approved