login
A116001
sigma(n) - phi(n) gives a semiprime (A001358).
2
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
EXAMPLE
sigma(100)-phi(100)=177=3*59
MATHEMATICA
Select[Range[600], PrimeOmega[DivisorSigma[1, #]-EulerPhi[#]]==2&] (* Harvey P. Dale, Mar 18 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Feb 13 2006
STATUS
approved