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Search: id:A074386
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| A074386 |
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Numbers n such that sigma(n) is the square of a prime. |
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+0
3
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OFFSET
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1,1
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COMMENT
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The next term, if it exists, is > 10^6.
The next term, if it exists, is > 10^7. - N. J. A. Sloane (njas(AT)research.att.com), May 26 2008
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EXAMPLE
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sigma[{3,81,400}]={4,121,961}.
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MATHEMATICA
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Do[s=DivisorSigma[1, n]; If[PrimeQ[Sqrt[s]], Print[n]], {n, 1, 1000000}] (Corrected by N. J. A. Sloane (njas(AT)research.att.com), May 26 2008)
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CROSSREFS
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Cf. A000203, A001248, A023194, A028982.
Sequence in context: A011187 A137994 A153709 this_sequence A116009 A068562 A123656
Adjacent sequences: A074383 A074384 A074385 this_sequence A074387 A074388 A074389
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KEYWORD
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nonn,bref,more
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Aug 22 2002
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EXTENSIONS
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Definition corrected by Juan Lopez, May 26, 2008
Edited by N. J. A. Sloane (njas(AT)research.att.com), May 26 2008
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