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A174331 n such that tau(Fibonacci(n)) is a perfect square. 1
1, 2, 6, 8, 9, 10, 14, 18, 19, 20, 22, 26, 27, 28, 30, 31, 32, 34, 40, 41, 42, 52, 53, 55, 59, 61, 64, 66, 71, 73, 74, 77, 79, 85, 87, 89, 92, 93, 94, 95, 97, 99, 101, 107, 109, 113, 115, 116, 117, 120, 121, 123, 125, 127, 128, 129, 130, 133, 135, 138, 143, 146, 147, 149 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

tau = A000005 is the number of divisors of n.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..423

FORMULA

{n: A063375(n) in A000290}. - R. J. Mathar, Jul 09 2012

EXAMPLE

40 is in the sequence because tau(Fibonacci(40)) = tau(102334155) = 64 is square.

MATHEMATICA

Select[Range[150], IntegerQ[Sqrt[DivisorSigma[0, Fibonacci[#]]]] &]

PROG

(PARI) is(n) = issquare(numdiv(fibonacci(n))) \\ Felix Fröhlich, Sep 08 2019

CROSSREFS

Cf. A000005, A000045, A000290, A036436, A063375.

Sequence in context: A120736 A130099 A047397 * A220116 A043341 A023714

Adjacent sequences:  A174328 A174329 A174330 * A174332 A174333 A174334

KEYWORD

nonn

AUTHOR

Michel Lagneau, Mar 15 2010

STATUS

approved

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Last modified June 18 07:11 EDT 2021. Contains 345098 sequences. (Running on oeis4.)