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%I #6 Apr 13 2021 23:53:06
%S 0,0,1,1,1,2,1,2,2,2,1,-1,1,2,3,3,1,4,2,4,3,2,1,-1,-1,2,4,4,1,6,2,4,3,
%T 2,3,-1,3,3,3,6,2,6,1,5,5,3,1,-1,3,-1,3,4,2,7,4,-1,5,3,2,-1,2,3,5,6,3,
%U 6,3,5,5,7,2,-1,2,4,-1,5,4,7,2,9,7,3,1,-1,4,3,4,9,2,11,-1,6,4,2,6,-1,4,5,6,-1,2,7,3,7,7,3,2,-1,2,-1,5,-1,2,9,4,6,6,5,3
%N Base-2 logarithm of the number of divisors of Fibonacci(n) if that number is a power of 2, otherwise -1.
%C It appears that the number of divisors of most Fibonacci numbers is a power of 2.
%e F(6)=8 has 4 divisors {1,2,4,8}, so a(6) = log_2(4) = 2.
%Y Cf. A081979.
%K sign
%O 1,6
%A _John W. Layman_, May 03 2005
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