A116000 phi(n) + sigma(n) gives a semiprime (A001358).
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
Keywords
Examples
phi(101)+sigma(101)=202=2*101.
Programs
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Mathematica
Select[Range[200],PrimeOmega[EulerPhi[#]+DivisorSigma[1,#]]==2&] (* Harvey P. Dale, Feb 05 2013 *)