A157345 Semiprimes that are the product of two distinct non-Sophie Germain primes.

91, 119, 133, 217, 221, 247, 259, 301, 323, 329, 403, 413, 427, 469, 481, 497, 511, 527, 553, 559, 589, 611, 629, 679, 703, 707, 721, 731, 749, 763, 767, 793, 799, 817, 871, 889, 893, 923, 949, 959, 973, 1003, 1027, 1037, 1043, 1057, 1099, 1121, 1139, 1141

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Feb 27 2009

Keywords

• nonn

Comments

91 = 7*13; 7 and 13 are not Sophie Germain primes, ...

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A001358, A005384, A111206, A157342, A006881, A157344.

Programs

Mathematica

lst={};Do[If[Plus@@Last/@FactorInteger[n]==2,a=Length[First/@FactorInteger[n]];If[a==2,b=First/@FactorInteger[n];c=b[[1]];d=b[[2]];If[ !PrimeQ[2*c+1]&&!PrimeQ[2*d+1],AppendTo[lst,n]]]],{n,7!}];lst
With[{nn=50},Take[Union[Times@@@Subsets[Select[Prime[Range[nn]], !PrimeQ[ 2#+1]&],{2}]],nn]] (* Harvey P. Dale, May 04 2015 *)