A174240 The multiplicative order of 2 mod n, where n an odd squarefree semiprime (A046388).

4, 6, 10, 12, 12, 8, 20, 18, 12, 22, 30, 8, 28, 12, 10, 36, 36, 44, 24, 20, 14, 18, 46, 60, 28, 20, 52, 33, 58, 60, 36, 40, 66, 84, 20, 90, 70, 28, 15, 18, 24, 92, 78, 36, 82, 110, 36, 52, 22, 60, 48, 116, 132, 42, 100, 60, 102, 140, 106, 72, 36, 69, 132, 28

Offset

1,1

Links

Vassilis Papadimitriou, Table of n, a(n) for n = 1..10000.

Formula

a(n) = A002326((A046388(n)+1)/2). - Amiram Eldar, Feb 24 2021

Example

For n = 1, a(1) = 4 is the multiplicative order of 2 mod 15 (15 is the first odd squarefree semiprime).

Mathematica

MultiplicativeOrder[2, #] & /@ Select[Range[1, 350, 2], PrimeOmega[#] == 2 && PrimeNu[#] == 2 &] (* Amiram Eldar, Feb 24 2021 *)

Prog

(PARI) lista(nn) = {forstep(n=1, nn, 2, if ((bigomega(n) == 2) && (omega(n)==2), print1(znorder(Mod(2, n)), ", ")); ); } \\ Michel Marcus, Feb 05 2015

Crossrefs

Cf. A002326, A046388.

Sequence in context: A184923 A137877 A246022 * A328321 A287342 A309177

Adjacent sequences: A174237 A174238 A174239 * A174241 A174242 A174243

Keyword

nonn

Author

Vassilis Papadimitriou, Mar 13 2010

Extensions

Edited by Ray Chandler, Jan 09 2012

Status

approved