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Search: id:A065820
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| A065820 |
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Numbers n such that Sigma6(n)/Sigma2(n) is prime. |
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+0
1
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| 2, 3, 5, 13, 17, 31, 43, 61, 83, 109, 131, 229, 239, 257, 263, 269, 311, 313, 443, 463, 503, 571, 593, 599, 619, 641, 647, 653, 659, 701, 797, 811, 853, 953, 967, 1009, 1031, 1039, 1063, 1123, 1373, 1459, 1483, 1499, 1663, 1669, 1693, 1733, 1741, 1759, 1789
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
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All entries are themselves prime.
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MATHEMATICA
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Select[Range[1, 2000 ], PrimeQ[( DivisorSigma[6, # ])/DivisorSigma[2, # ]] & ]
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PROGRAM
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(PARI) { n=0; for (m=1, 10^9, f=sigma(m, 6)/sigma(m, 2); if (frac(f) == 0 && isprime(f), write("b065820.txt", n++, " ", m); if (n==1000, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 31 2009]
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CROSSREFS
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Sequence in context: A154554 A105879 A066111 this_sequence A163268 A108562 A087523
Adjacent sequences: A065817 A065818 A065819 this_sequence A065821 A065822 A065823
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 06 2001
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