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A157347 Products of 3 distinct non-Sophie Germain primes. 7
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

1547=7*13*17; 7,13 and 17 are not Sophie Germain primes,...

LINKS

Table of n, a(n) for n=1..42.

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

PROG

(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; [From Klaus Brockhaus, Apr 11 2009]

CROSSREFS

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

Sequence in context: A246899 A090209 A283154 * A255356 A020408 A259424

Adjacent sequences:  A157344 A157345 A157346 * A157348 A157349 A157350

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Feb 27 2009

EXTENSIONS

Entries verified by Klaus Brockhaus, Apr 11 2009

STATUS

approved

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Last modified June 25 11:59 EDT 2017. Contains 288710 sequences.