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%I #3 May 01 2014 02:43:29
%S 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,
%T 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,
%U 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10
%N 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.
%C An approximate "inverse" of A000045 (of the Fibonacci numbers).
%p [seq(floor(log[(sqrt(5)+1)/2](n*sqrt(5))),n=1..120)];
%o (Scheme function:) (define (A072648 n) (cond ((zero? n) n) (else (floor->exact (/ (log (* n *Sqrt5*)) *LogPhi*)))))
%o (define *Sqrt5* (sqrt 5))
%o (define *Phi* (/ (1+ *Sqrt5*) 2))
%o (define *LogPhi* (log *Phi*))
%Y Used to construct A072649.
%K nonn
%O 1,2
%A _Antti Karttunen_, Jun 02 2002
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