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A116000
phi(n) + sigma(n) gives a semiprime (A001358).
1
2, 3, 4, 5, 6, 7, 10, 11, 13, 16, 17, 19, 22, 23, 25, 27, 29, 31, 37, 40, 41, 43, 46, 47, 52, 53, 58, 59, 61, 64, 67, 68, 71, 72, 73, 79, 80, 82, 83, 89, 97, 98, 101, 103, 106, 107, 109, 113, 117, 127, 128, 131, 136, 137, 139, 144, 149, 151, 157, 162, 163, 166, 167
OFFSET
1,1
EXAMPLE
phi(101)+sigma(101)=202=2*101.
MATHEMATICA
Select[Range[200], PrimeOmega[EulerPhi[#]+DivisorSigma[1, #]]==2&] (* Harvey P. Dale, Feb 05 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 13 2006
STATUS
approved