A269453 The order of 2 mod m when m is the product of two distinct safe primes.

12, 20, 30, 44, 33, 92, 110, 116, 69, 174, 164, 230, 212, 246, 290, 318, 332, 356, 410, 253, 452, 249, 530, 534, 524, 638, 678, 692, 716, 830, 393, 902, 764, 890, 932, 956, 1038, 1166, 1130, 537, 1004, 573, 1334, 1124, 1310, 1172, 1398, 717, 753, 1436, 1730, 913, 1886, 1686, 1790

Offset: 1

Author

Marina Ibrishimova, Feb 27 2016

Keywords

• nonn

Comments

The smallest positive integer k for which 2^k == 1 (mod m) where m = p*q with p, q distinct safe primes.

Crossrefs

Cf. A002326, A157352, A269452.

Programs

Mathematica

MultiplicativeOrder[2, #] & /@ Select[Select[Range@ 4200, PrimeNu@ # == 2 &], Times @@ Map[If[PrimeQ[(# - 1)/2], #, 0] &, Map[First, FactorInteger@ #]] == # &] (* Michael De Vlieger, Feb 28 2016 *)

Formula

a(n) is the order of 2 modulo A157352(n). - Wolfdieter Lang, Mar 31 2016

Extensions

More terms from Michael De Vlieger, Feb 28 2016