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A065817
Numbers n such that sigma_5(n)/sigma_1(n) is prime.
1
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
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[1, 3000 ], PrimeQ[( DivisorSigma[5, # ])/DivisorSigma[1, # ]] & ]
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)) ) } \\ Harry J. Smith, Oct 31 2009
CROSSREFS
Sequence in context: A333612 A362025 A093305 * A361227 A084542 A038201
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Dec 06 2001
STATUS
approved