A176262 Numbers of the form 3k+1 with greatest prime divisor of the form 3m-1.

4, 10, 16, 22, 25, 34, 40, 46, 55, 58, 64, 82, 85, 88, 94, 100, 106, 115, 118, 121, 136, 142, 145, 154, 160, 166, 178, 184, 187, 202, 205, 214, 220, 226, 232, 235, 238, 250, 253, 256, 262, 265, 274, 289, 295, 298, 319, 322, 328, 334, 340, 346, 352, 355, 358, 376

Offset: 1

Author

Vladimir Shevelev, Apr 13 2010

Keywords

• nonn

Comments

All numbers of the form 2p, where p==2(mod 3) is prime, are in the sequence.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A176258, A176257, A176256, A176255, A002148, A002145, A016813, A004767.

Programs

Mathematica

Select[3 Range@ 120 + 1, Mod[#, 3] == 2 &[FactorInteger[#][[-1, 1]]] &] (* Michael De Vlieger, Feb 07 2016 *)

PARI

isok(n) = ((n % 3) == 1) && (n != 1) && ((vecmax(factor(n)[,1]) % 3) == 2); \\ Michel Marcus, Feb 07 2016

Extensions

Corrected and extended by Michel Marcus, Feb 07 2016