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Search: id:A065817
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| A065817 |
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Numbers n such that Sigma5(n)/Sigma1(n) is prime. |
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+0
1
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| 2, 3, 4, 5, 9, 11, 37, 43, 47, 71, 121, 131, 157, 223, 251, 257, 289, 307, 487, 529, 641, 1087, 1093, 1187, 1291, 1433, 1567, 1621, 1637, 1831, 1849, 1873, 1901, 2017, 2111, 2143, 2293, 2333, 2473, 2621, 2663, 2683, 2707, 2777, 2809, 2843, 2903, 3257, 3413
(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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MATHEMATICA
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Select[Range[1, 3000 ], PrimeQ[( DivisorSigma[5, # ])/DivisorSigma[1, # ]] & ]
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PROGRAM
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(PARI) { n=0; for (m=1, 10^9, f=sigma(m, 5)/sigma(m); if (frac(f) == 0 && isprime(f), write("b065817.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: A100797 A139441 A093305 this_sequence A084542 A038201 A033084
Adjacent sequences: A065814 A065815 A065816 this_sequence A065818 A065819 A065820
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KEYWORD
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nonn,new
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 06 2001
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