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
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