OFFSET
1,2
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..500
MATHEMATICA
Select[ Range[ 10^7 ], DivisorSigma[ 1, EulerPhi[ # ] ] == EulerPhi[ DivisorSigma[ 1, # ] ] && Union[ Transpose[ FactorInteger[ # ] ] [ [ 2 ] ] ] == {1} & ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Dec 26 2000
EXTENSIONS
Prepended missing a(1)=1, Donovan Johnson, Mar 03 2012.
STATUS
approved