login
A005908
a(n) = floor( phi*a(n-1) ) + floor( phi*a(n-2) ), where phi is the golden ratio.
1
0, 1, 1, 2, 4, 9, 20, 46, 106, 245, 567, 1313, 3041, 7044, 16317, 37798, 87559, 202831, 469860, 1088436, 2521375, 5840796, 13530276, 31343052, 72606569, 168194019, 389623535, 902567761, 2090809436, 4843386045
OFFSET
0,4
LINKS
FORMULA
Limit_{n -> infinity} a(n)/a(n-1) = phi/C = 2.31651242917313... where phi is the golden ratio and C the positive root of x^4 + x^3 - 2*x^2 - 2*x - 1 (C = 0.6984784404...). - Benoit Cloitre, Aug 13 2002
Conjectures from Chai Wah Wu, Jun 13 2020: (Start)
a(n) = 2*a(n-1) + a(n-2) - a(n-4) - a(n-5) for n > 4.
G.f.: x*(-x^3 - x^2 - x + 1)/(x^5 + x^4 - x^2 - 2*x + 1). (End)
MATHEMATICA
nxt[{a_, b_}]:={b, Floor[GoldenRatio*a]+Floor[GoldenRatio*b]}; Transpose[ NestList[ nxt, {0, 1}, 30]][[1]] (* Harvey P. Dale, Apr 24 2016 *)
CROSSREFS
Cf. A001622 (golden ratio).
Sequence in context: A191653 A191827 A000968 * A206119 A085748 A317097
KEYWORD
nonn
STATUS
approved