A296243 - OEIS

A296243

Numbers k such that the multiplicative order of 2 modulo k is even.

3, 5, 9, 11, 13, 15, 17, 19, 21, 25, 27, 29, 33, 35, 37, 39, 41, 43, 45, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 75, 77, 81, 83, 85, 87, 91, 93, 95, 97, 99, 101, 105, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149, 153

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OFFSET

1,1

COMMENTS

Odd numbers k such that A007733(k) = A002326((k-1)/2) is even.

LINKS

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

MATHEMATICA

A036259 = Select[Range[1, 199, 2], OddQ[MultiplicativeOrder[2, #]] &];

Range[1, A036259[[-1]], 2] ~Complement~ A036259 (* Jean-François Alcover, Dec 20 2017 *)

Select[Range[1, 153, 2], EvenQ[MultiplicativeOrder[2, #]] &] (* Amiram Eldar, Jul 30 2020 *)

PROG