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 A072648 a(n) = [log_{Phi}(n*sqrt(5))], where log_{Phi} is logarithm in the base Phi ( = (sqrt(5)+1)/2) and [] stands for the floor function. 2
 1, 3, 3, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS An approximate "inverse" of A000045 (of the Fibonacci numbers). LINKS MAPLE [seq(floor(log[(sqrt(5)+1)/2](n*sqrt(5))), n=1..120)]; PROG (Scheme function:) (define (A072648 n) (cond ((zero? n) n) (else (floor->exact (/ (log (* n *Sqrt5*)) *LogPhi*))))) (define *Sqrt5* (sqrt 5)) (define *Phi* (/ (1+ *Sqrt5*) 2)) (define *LogPhi* (log *Phi*)) CROSSREFS Used to construct A072649. Sequence in context: A196337 A064631 A298200 * A185585 A072945 A274004 Adjacent sequences:  A072645 A072646 A072647 * A072649 A072650 A072651 KEYWORD nonn AUTHOR Antti Karttunen, Jun 02 2002 STATUS approved

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Last modified March 18 17:51 EDT 2019. Contains 321292 sequences. (Running on oeis4.)