A157347 Products of 3 distinct non-Sophie Germain primes.

1547, 1729, 2261, 2821, 3367, 3689, 3913, 4123, 4199, 4277, 4403, 4921, 5117, 5369, 5551, 5593, 5719, 6097, 6251, 6461, 6643, 6851, 7021, 7189, 7259, 7657, 7847, 7973, 8029, 8113, 8177, 8449, 8687, 8827, 8911, 9139, 9191, 9331, 9373, 9401, 9443, 9503

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Feb 27 2009

Keywords

• nonn

Examples

			1547 = 7*13*17 is a term: its prime factors 7, 13, and 17 are not Sophie Germain primes.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..5600

Crossrefs

Cf. A001358, A005384, A111206, A157342, A006881, A157344, A157345, A007304, A157346.

Programs

Magma

S:=[ p: p in PrimesUpTo(120) | not IsPrime(2*p+1) ]; T:=[ q: a, b, c in S | a lt b and b lt c and q lt 10000 where q is a*b*c ]; Sort(~T); T; // Klaus Brockhaus, Apr 11 2009

Mathematica

lst={};Do[If[Plus@@Last/@FactorInteger[n]==3,a=Length[First/@FactorInteger[n]];If[a==3,b=First/@FactorInteger[n];c=b[[1]];d=b[[2]];e=b[[3]];If[ !PrimeQ[2*c+1]&&!PrimeQ[2*d+1]&&!PrimeQ[2*e+1],AppendTo[lst,n]]]],{n,8!}];lst

Extensions

Entries verified by Klaus Brockhaus, Apr 11 2009