A176312 Numbers that are the products of two single (or isolated or non-twin) primes.

4, 46, 74, 94, 106, 134, 158, 166, 178, 194, 226, 254, 262, 314, 326, 334, 346, 422, 446, 466, 502, 514, 526, 529, 554, 586, 614, 634, 662, 674, 706, 718, 734, 746, 758, 766, 778, 794, 802, 818, 851, 878, 886, 898, 914, 934, 958, 974, 982, 998, 1006, 1018, 1081

Offset: 1

Author

Juri-Stepan Gerasimov, Apr 15 2010

Keywords

• nonn

Links

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

Crossrefs

Cf. A007510.

Programs

Maple

isA007510 := proc(n) isprime(n) and not isprime(n+2) and not isprime(n-2) ; simplify(%) ; end proc:
isA176312 := proc(n) for d in numtheory[divisors](n) do if isA007510(d) and isA007510(n/d) then return true; end if; end do: return false; end proc:
for n from 1 to 1200 do if isA176312(n) then printf("%d,",n) ; end if; end do: # R. J. Mathar, Apr 20 2010:

Mathematica

Select[Range[1000], PrimeOmega[#] == 2 && AllTrue[FactorInteger[#][[;;, 1]], ! PrimeQ[#1 - 2] && ! PrimeQ[#1 + 2] &] &] (* Amiram Eldar, Nov 30 2020 *)

Extensions

Entries checked by R. J. Mathar, Apr 20 2010