A116001 sigma(n) - phi(n) gives a semiprime (A001358).

6, 10, 18, 20, 22, 27, 34, 40, 49, 52, 58, 64, 68, 82, 98, 100, 118, 136, 142, 144, 148, 160, 162, 164, 202, 212, 214, 242, 243, 244, 274, 288, 289, 298, 320, 325, 333, 338, 343, 356, 358, 361, 382, 392, 394, 404, 436, 441, 454, 464, 478, 512, 538, 544, 548

Offset: 1

Author

Giovanni Resta, Feb 13 2006

Keywords

• nonn

Examples

			sigma(100)-phi(100)=177=3*59
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001358, A116017, A116000.

Programs

Mathematica

Select[Range[600],PrimeOmega[DivisorSigma[1,#]-EulerPhi[#]]==2&] (* Harvey P. Dale, Mar 18 2013 *)