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A135978
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Primes p such that 2^p-1 has exactly 2 prime factors.
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4
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11, 23, 37, 41, 59, 67, 83, 97, 101, 103, 109, 131, 137, 139, 149, 167, 197, 199, 227, 241, 269, 271, 281, 293, 347, 373, 379, 421, 457, 487, 523, 727, 809, 881, 971, 983, 997
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| k = {}; Do[If[ ! PrimeQ[2^Prime[n] - 1], c = FactorInteger[2^Prime[n] - 1]; d = Length[c]; If[d == 2, AppendTo[k, Prime[n]]]], {n, 1, 40}]; k
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CROSSREFS
| Cf. A000225, A065341, A054723, A134852, A135975, A135976, A135977.
Sequence in context: A101859 A079664 A160268 * A139493 A077345 A130282
Adjacent sequences: A135975 A135976 A135977 * A135979 A135980 A135981
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KEYWORD
| nonn
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AUTHOR
| Artur Jasinski (grafix(AT)csl.pl), Dec 09 2007
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EXTENSIONS
| a(17)-a(37) from Arkadiusz Wesolowski, Jan 26 2012
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