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This question is related to sequence of numbers $t$ such that $F_{6t}$ is a nontotient where $F_n$ represents the sequence of Fibonacci numbers for $n\geq 0$.

The online encyclopedia Wikipedia has the articles Fibonacci number and Nontotient, respectively.

There are very few terms in https://oeis.org/A335976 and some prime numbers appear as initial terms as expected.

Conjecture. There are infinitely many numbers $t$ such that $F_{6t}$ is a nontotient.

Question. Can someone prove or disprove above conjecture?

Initial terms of sequence of composite numbers $t_{c}$ such that $F_{6t_{c}}$ is a nontotient are also very welcome as helpful comment. Additionally, I couldn't find that question in literature yet, but if one can find references that have these or strongly related results, I will be very grateful for this response.

Thanks.

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  • $\begingroup$ Why in particular $F_{6t}$? Why not all $F_n$? $\endgroup$ Aug 2, 2020 at 23:41
  • $\begingroup$ Because only $6t$ indices can be totient except beginning of sequence. $\endgroup$
    – Alkan
    Aug 3, 2020 at 5:32

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