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A157345 Semiprimes that are the product of two distinct non-Sophie Germain primes. 8
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..50.

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 *)

CROSSREFS

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

Sequence in context: A161945 A140389 A236845 * A092125 A005935 A020307

Adjacent sequences:  A157342 A157343 A157344 * A157346 A157347 A157348

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Feb 27 2009

STATUS

approved

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Last modified June 27 21:39 EDT 2017. Contains 288804 sequences.