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A336655 Odd numbers k such that the multiplicative order of 2 modulo k is squarefree. 3
1, 3, 7, 9, 11, 21, 23, 31, 33, 43, 47, 49, 59, 63, 67, 69, 71, 77, 79, 83, 89, 93, 99, 103, 107, 121, 127, 129, 131, 139, 141, 147, 151, 161, 167, 177, 179, 191, 201, 207, 211, 213, 217, 223, 227, 231, 233, 237, 239, 249, 253, 263, 267, 279, 281, 283, 301, 307 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

Francesco Pappalardi, Square free values of the order function, New York J. Math., Vol. 9 (2003), pp. 331-344.

FORMULA

The number of terms not exceeding x is (a + o(1))* x * log(x)^(b-1), where a and b (~ 0.46437) are constants (Pappalardi, 2003).

EXAMPLE

3 is a term since the multiplicative order of 2 modulo 3 is 2 which is squarefree.

MATHEMATICA

Select[2 * Range[160] - 1, SquareFreeQ[MultiplicativeOrder[2, #]] &]

PROG

(PARI) isok(k) = (k % 2) && issquarefree(znorder(Mod(2, k))); \\ Michel Marcus, Jul 29 2020

CROSSREFS

Cf. A002326, A005117, A049149, A336654, A336656.

Sequence in context: A167800 A270834 A192628 * A003538 A018596 A191181

Adjacent sequences:  A336652 A336653 A336654 * A336656 A336657 A336658

KEYWORD

nonn

AUTHOR

Amiram Eldar, Jul 28 2020

STATUS

approved

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Last modified October 1 22:45 EDT 2022. Contains 357173 sequences. (Running on oeis4.)