A093335 a(0) = 1, a(1) = 1 and for n >= 2, a(n) = floor(4 * a(n-2) * a(n-1) / (a(n-2) + a(n-1))).

1, 1, 2, 2, 4, 5, 8, 12, 19, 29, 45, 70, 109, 170, 265, 414, 646, 1009, 1575, 2460, 3840, 5997, 9364, 14622, 22833, 35654, 55676, 86940, 135762, 211998, 331047, 516946, 807239, 1260545, 1968408, 3073772, 4799858, 7495231, 11704199, 18276724

Offset

0,3

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Example

a(5) = 5 because a(5) = floor(4*a(3)*a(4)/(a(3)+a(4))) = floor(4*2*4/(2+4)) = floor(32/6) = 5.

Mathematica

nxt[{a_, b_}]:={b, Floor[2*HarmonicMean[{a, b}]]}; Join[{1}, Transpose[ NestList[ nxt, {1, 2}, 40]][[1]]] (* Harvey P. Dale, Mar 04 2015 *)

Crossrefs

Cf. A093333, A093332.

Sequence in context: A274154 A274153 A079501 * A093333 A116085 A329692

Adjacent sequences: A093332 A093333 A093334 * A093336 A093337 A093338

Keyword

easy,nonn,changed

Author

Robert A. Stump (rstump_2004(AT)yahoo.com), Apr 25 2004

Extensions

Definition corrected by Jason Yuen, Aug 27 2024

Status

approved