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A066171
Numbers n such that d(n) = phi(n+1) - phi(n), where d(n) denotes the number of divisors of n.
0
6, 74, 315, 344, 5313, 17534, 23655, 27027, 46035, 54494, 56865, 139814, 13437105, 454166115, 2403502647, 4590102525, 38645268615, 96891671331
OFFSET
1,1
COMMENTS
These are the n at which phi(n) is increasing at a rate equal to d(n).
a(19) > 2*10^11. - Donovan Johnson, Jun 23 2010
EXAMPLE
d(74) = 4 = 40 - 36 = phi(75) - phi(74).
MATHEMATICA
Select[ Range[ 1, 10^6 ], EulerPhi[ # + 1 ] - EulerPhi[ # ] == DivisorSigma[ 0, # ] & ]
CROSSREFS
Sequence in context: A168603 A244689 A058793 * A269647 A232330 A269337
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Dec 14 2001
EXTENSIONS
a(13) from Harry J. Smith, Feb 04 2010
a(14)-a(18) from Donovan Johnson, Jun 23 2010
STATUS
approved