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A158914
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Primes p such that there is a composite c with sigma_2(p)=sigma_2(c).
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1
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OFFSET
| 1,1
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COMMENTS
| No other terms less than 10^8. The corresponding composite numbers are 6, 40, 136, and 3352. Is this sequence finite? See A158913 for the sequence for sigma_1.
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MATHEMATICA
| tp=DivisorSigma[2, Select[Range[4000], PrimeQ]]; tc=DivisorSigma[2, Select[Range[4000], !PrimeQ[ # ]&]]; Sqrt[Intersection[tp, tc]-1]
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CROSSREFS
| Sequence in context: A139916 A009219 A142185 * A046872 A167860 A152988
Adjacent sequences: A158911 A158912 A158913 * A158915 A158916 A158917
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KEYWORD
| more,nonn
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Mar 30 2009
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