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A067738
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Numbers k such that sigma(k) + sigma(sigma(k)) is prime.
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1
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1, 2, 3, 7, 22, 32, 49, 52, 66, 70, 93, 94, 97, 98, 115, 119, 121, 127, 169, 170, 196, 214, 241, 242, 256, 265, 337, 343, 364, 441, 450, 513, 529, 567, 577, 578, 597, 679, 723, 784, 800, 841, 967, 1058, 1225, 1249, 1369, 1444, 1521, 1682, 1731, 1802, 1849
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range[2000], PrimeQ[DivisorSigma[1, #]+DivisorSigma[1, DivisorSigma[ 1, #]]]&] (* Harvey P. Dale, Apr 02 2018 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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