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

Author

Vassilis Papadimitriou, Mar 13 2010

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Cf. A002326, A046388.

Programs

Mathematica

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

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

Formula

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

Extensions

Edited by Ray Chandler, Jan 09 2012