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A105307
Base-2 logarithm of the number of divisors of Fibonacci(n) if that number is a power of 2, otherwise -1.
1
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, 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, 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
OFFSET
1,6
COMMENTS
It appears that the number of divisors of most Fibonacci numbers is a power of 2.
EXAMPLE
F(6)=8 has 4 divisors {1,2,4,8}, so a(6) = log_2(4) = 2.
CROSSREFS
Cf. A081979.
Sequence in context: A026513 A349497 A106028 * A281012 A347342 A304943
KEYWORD
sign
AUTHOR
John W. Layman, May 03 2005
STATUS
approved