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Search: id:A072282
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| A072282 |
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Numbers n such that sigma(n) + 1 and sigma(n) - 1 are twin primes. |
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+0
1
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| 3, 5, 6, 10, 11, 17, 20, 24, 26, 29, 30, 38, 41, 46, 51, 55, 59, 71, 85, 88, 101, 105, 107, 114, 118, 126, 135, 136, 137, 141, 145, 147, 149, 155, 158, 161, 177, 178, 179, 185, 191, 197
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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sigma(20) + 1 = 43 and sigma(20) - 1 = 41, so 20 is a term of the sequence.
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MATHEMATICA
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Select[Range[10^3], PrimeQ[DivisorSigma[1, # ] + 1] && PrimeQ[DivisorSigma[1, # ] - 1] &]
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CROSSREFS
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Adjacent sequences: A072279 A072280 A072281 this_sequence A072283 A072284 A072285
Sequence in context: A066147 A140951 A065873 this_sequence A047327 A028927 A099190
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KEYWORD
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easy,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jul 10 2002
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