A015800 Numbers k such that phi(k) + 9 | sigma(k).

26, 312, 828, 2475, 2520, 4950, 7412, 7942, 10464, 14454, 30952, 89262, 1029632, 3116544, 17721152, 56889152, 538655552, 804839424, 9287924224, 206150959104, 698155922432

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Comments

a(22) > 10^12. - Donovan Johnson, Feb 28 2012

Programs

Mathematica

Cases[Range[100000],
x_ /; Divisible[DivisorSigma[1, x], EulerPhi[x] + 9] == True] (* David Nacin, Feb 28 2012 *)
Select[Range[1000000],Divisible[DivisorSigma[1,#],EulerPhi[#]+9]&] (* Harvey P. Dale, May 24 2012 *)

Extensions

a(9)-a(21) from Donovan Johnson, Feb 28 2012