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A066171
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Numbers n such that d(n) = EulerPhi(n+1) - EulerPhi(n), where d(n) denotes the number of divisors of n.
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0
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6, 74, 315, 344, 5313, 17534, 23655, 27027, 46035, 54494, 56865, 139814, 13437105, 454166115, 2403502647, 4590102525, 38645268615, 96891671331
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OFFSET
| 1,1
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COMMENTS
| These are the n at which EulerPhi(n) is increasing at a rate equal to d(n).
a(19) > 2*10^11. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 23 2010]
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EXAMPLE
| d(74) = 4 = 40 - 36 = EulerPhi(75) - EulerPhi(74).
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MATHEMATICA
| Select[ Range[ 1, 10^6 ], EulerPhi[ # + 1 ] - EulerPhi[ # ] == DivisorSigma[ 0, # ] & ]
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CROSSREFS
| Sequence in context: A135594 A168603 A058793 * A057783 A177561 A069852
Adjacent sequences: A066168 A066169 A066170 * A066172 A066173 A066174
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KEYWORD
| nonn
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AUTHOR
| Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 14 2001
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EXTENSIONS
| a(13) from Harry J. Smith (hjsmithh(AT)sbcglobal.net), Feb 04 2010
a(14)-a(18) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jun 23 2010
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