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

1,1

Links

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

Example

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

Mathematica

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

Crossrefs

Cf. A001358, A116017, A116000.

Sequence in context: A020718 A048587 A351661 * A111617 A315359 A361464

Adjacent sequences: A115998 A115999 A116000 * A116002 A116003 A116004

Keyword

nonn

Author

Giovanni Resta, Feb 13 2006

Status

approved