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A142337
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Numbers n such that sum(i=1..n, sigma(i)) is prime.
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0
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7, 12, 18, 23, 24, 32, 49, 66, 84, 87, 90, 92, 111, 112, 113, 114, 129, 130, 132, 133, 137, 138, 199, 238, 239, 271, 275, 278, 283, 285, 307, 313, 314, 317, 319, 322, 340, 342, 352, 357, 392, 394, 397, 399, 442, 443, 491, 492, 494, 499, 500, 619, 622, 648, 649
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Numbers n such that A024916(n) is prime.
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MATHEMATICA
| Flatten[Table[If[PrimeQ[Sum[DivisorSigma[1, i], {i, 1, n}]], n, {}], {n, 1, 300}]].
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PROG
| (PARI) t=0; for(n=1, 1e3, if(isprime(t+=sigma(n)), print1(n", "))) \\ Charles R Greathouse IV, Nov 07 2011
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CROSSREFS
| Cf. A024916.
Sequence in context: A183046 A092094 A064665 * A131912 A022953 A030714
Adjacent sequences: A142334 A142335 A142336 * A142338 A142339 A142340
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KEYWORD
| nonn
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AUTHOR
| Roger L. Bagula and Gary W. Adamson (rlbagulatftn(AT)yahoo.com), Sep 18 2008
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