A043326 Numbers k such that k is a product of two different primes and k-2 is prime.

15, 21, 33, 39, 55, 69, 85, 91, 111, 115, 129, 133, 141, 159, 183, 201, 213, 235, 253, 259, 265, 295, 309, 319, 339, 355, 381, 391, 403, 411, 445, 451, 469, 481, 489, 493, 501, 505, 511, 543, 559, 565, 573, 579, 589, 633, 649, 655, 679, 685

Offset: 1

Author

Olivier Gérard, Jul 19 2001

Keywords

• nonn

Links

• Zak Seidov and Michael De Vlieger, Table of n, a(n) for n = 1..21728 (first 10000 terms from Zak Seidov)

Crossrefs

Cf. A006512, A062721.

Subsequence of A006881.

Programs

Mathematica

Select[Range[700],PrimeOmega[#]==PrimeNu[#]==2&&PrimeQ[#-2]&] (* Harvey P. Dale, Feb 01 2014 *)
Select[Prime[Range[200]]+2,PrimeOmega[#]==PrimeNu[#]==2&] (* Harvey P. Dale, Oct 13 2018 *)

PARI

is(n)=isprime(n-2) && bigomega(n)==2 && !issquare(n) \\ Charles R Greathouse IV, Jul 20 2014