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A118369
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Numbers n such that prod_{d|n} d + 1 is prime.
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3
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1, 2, 6, 10, 14, 24, 26, 54, 56, 74, 88, 94, 134, 146, 154, 174, 206, 238, 248, 266, 296, 314, 326, 328, 374, 378, 386, 430, 442, 466, 472, 488, 494, 498, 510, 568, 582, 584, 634, 674, 680, 710, 730, 742, 786, 856, 874, 894, 918, 962, 986, 1038, 1094, 1174
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| See A118370 for the corresponding primes, 'divisorial primes'.
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LINKS
| Paolo P. Lava, Table of n, a(n) for n = 1..10000
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EXAMPLE
| The (positive) divisors of 6 are 1,2,3,6. As 6*3*2*1 + 1 = 37 is prime, 6 is a term.
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MATHEMATICA
| f[n_]:=PrimeQ[Times@@Divisors[n]+1]; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 7!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 14 2009]
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PROG
| (PARI) for(n=1, 2500, s=1; fordiv(n, d, s=s*d); if(isprime(s+1), print1(n, ", ")))
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CROSSREFS
| Cf. A118370, A007955.
Sequence in context: A185548 A039956 A197930 * A082816 A074105 A179777
Adjacent sequences: A118366 A118367 A118368 * A118370 A118371 A118372
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KEYWORD
| nonn
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AUTHOR
| Rick L. Shepherd (rshepherd2(AT)hotmail.com), Apr 25 2006
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