A269452 phi(A157352(n)), n >= 1, where phi is Euler's totient function A000010, and A157352 gives the products of two distinct safe primes.

24, 40, 60, 88, 132, 184, 220, 232, 276, 348, 328, 460, 424, 492, 580, 636, 664, 712, 820, 1012, 904, 996, 1060, 1068, 1048, 1276, 1356, 1384, 1432, 1660, 1572, 1804, 1528, 1780, 1864, 1912, 2076, 2332, 2260, 2148, 2008, 2292, 2668, 2248, 2620, 2344, 2796, 2868, 3012, 2872, 3460, 3652, 3772, 3372

Offset: 1

Author

Marina Ibrishimova, Feb 27 2016

Keywords

• nonn

Comments

phi(p*q) = (p-1)(q-1) where p, q are distinct safe primes.

2^(a(n)/2) == 1 (mod A157352(n)). For the reference see a comment on A269454. - Wolfdieter Lang, Mar 31 2016

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1500

Crossrefs

Cf. A000010, A157352, A269454.

Programs

Mathematica

EulerPhi /@ Select[Select[Range@ 4000, PrimeNu@ # == 2 &], Times @@ Map[If[PrimeQ[(# - 1)/2], #, 0] &, Map[First, FactorInteger@ #]] == # &] (* Michael De Vlieger, Feb 28 2016 *)

Formula

a(n) = phi(A157352(n)), n >= 1.

Extensions

More terms from Michael De Vlieger, Feb 28 2016