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A071114
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Numbers n such that n and sigma(n) are prime powers (of the form p^k, p prime, k>=1).
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0
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2, 3, 4, 7, 9, 16, 25, 31, 64, 81, 127, 289, 729, 1681, 2401, 3481, 4096, 5041, 7921, 8191, 10201, 15625, 17161, 27889, 28561, 29929, 65536, 83521, 85849, 131071, 146689, 262144, 279841, 458329, 491401, 524287, 531441, 552049, 579121, 597529
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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MATHEMATICA
| Select[ Range[10^6], f[ # ] == f[ DivisorSigma[1, # ]] == 1 & ]
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PROG
| (PARI) for(n=1, 100000, if(omega(n)*omega(sigma(n)) == 1, print1(n, ", ")))
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CROSSREFS
| Sequence in context: A027947 A067236 A070763 * A078696 A098115 A182833
Adjacent sequences: A071111 A071112 A071113 * A071115 A071116 A071117
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), May 27 2002
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EXTENSIONS
| Edited by Robert G. Wilson v (rgwv(AT)rgwv.com) and David Wasserman (wasserma(AT)spawar.navy.mil), May 30 2002
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