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A119588 Numbers n such that the number of divisors of Fibonacci(n), tau(Fibonacci(n)), is not a perfect power of 2. 0
12, 24, 25, 36, 48, 50, 56, 60, 72, 75, 84, 91, 96, 100, 108, 110, 112, 120, 132, 144, 150, 153, 156, 168, 175, 180, 182, 192, 200, 204, 216, 220, 224, 225, 228, 240, 252, 264, 273, 275, 276, 280, 300, 306, 312, 324, 325, 330, 336, 342, 348, 350, 360, 364, 372 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Has many terms in common with A023172 (41 below 1000), but neither is a subsequence of the other since 125 is not in this sequence.

LINKS

Table of n, a(n) for n=1..55.

Blair Kelly, Fibonacci and Lucas Factorizations.

FORMULA

a(n) = {k: tau(Fibonacci(k)) != 2^i for all i}.

EXAMPLE

F(12) = 144 has 15 divisors: {1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 36, 48, 72, 144}. Since 15 is not a power of 2, 12 is in the sequence.

F(24) = 46368 has 72 divisors. Since 72 is not a power of 2, 24 is in the sequence.

MATHEMATICA

Do[If[ !IntegerQ[Log[2, DivisorSigma[0, Fibonacci[n]]]], Print[n]], {n, 10^3}]

CROSSREFS

Sequence in context: A296749 A297276 A095780 * A167994 A065303 A239673

Adjacent sequences:  A119585 A119586 A119587 * A119589 A119590 A119591

KEYWORD

nonn

AUTHOR

Ryan Propper, Jun 01 2006

STATUS

approved

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Last modified September 16 07:19 EDT 2021. Contains 347469 sequences. (Running on oeis4.)