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A157344 Semiprimes that are the product of two distinct Sophie Germain primes. 11
6, 10, 15, 22, 33, 46, 55, 58, 69, 82, 87, 106, 115, 123, 145, 159, 166, 178, 205, 226, 249, 253, 262, 265, 267, 319, 339, 346, 358, 382, 393, 415, 445, 451, 466, 478, 502, 519, 537, 562, 565, 573, 583, 586, 655, 667, 699, 717, 718, 753, 838, 843, 862, 865 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
6=2*3; 2 and 3 are Sophie Germain primes, 10=2*5; 2 and 5 are Sophie Germain primes, 15=3*5; 3 and 5 are Sophie Germain primes, ...
LINKS
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
nn=100; With[{sgp=Select[Prime[Range[nn]], PrimeQ[2#+1]&]}, Take[ Union[ Select[ Times @@@ Subsets[sgp, {2}], PrimeOmega[#]==2&]], nn]] (* Harvey P. Dale, Nov 22 2012 *)
CROSSREFS
Sequence in context: A022949 A049694 A285766 * A332765 A093773 A088708
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified March 28 13:35 EDT 2024. Contains 371254 sequences. (Running on oeis4.)