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A174240 The multiplicative order of 2 mod n, where n an odd squarefree semiprime (A046388). 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified July 24 20:26 EDT 2021. Contains 346273 sequences. (Running on oeis4.)