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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 (list; graph; refs; listen; history; text; internal format)
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 A344882

Adjacent sequences:  A115998 A115999 A116000 * A116002 A116003 A116004

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 13 2006

STATUS

approved

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Last modified August 19 18:30 EDT 2022. Contains 356229 sequences. (Running on oeis4.)