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A065817
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Numbers n such that Sigma5(n)/Sigma1(n) is prime.
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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; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
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MATHEMATICA
| Select[Range[1, 3000 ], PrimeQ[( DivisorSigma[5, # ])/DivisorSigma[1, # ]] & ]
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PROG
| (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
| Sequence in context: A100797 A139441 A093305 * A084542 A038201 A033084
Adjacent sequences: A065814 A065815 A065816 * A065818 A065819 A065820
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 06 2001
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