A015800 - OEIS

%I #20 Sep 08 2019 20:06:28

%S 26,312,828,2475,2520,4950,7412,7942,10464,14454,30952,89262,1029632,

%T 3116544,17721152,56889152,538655552,804839424,9287924224,

%U 206150959104,698155922432

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

%C a(22) > 10^12. - _Donovan Johnson_, Feb 28 2012

%t Cases[Range[100000],

%t x_ /; Divisible[DivisorSigma[1, x], EulerPhi[x] + 9] == True] (* _David Nacin_, Feb 28 2012 *)

%t Select[Range[1000000],Divisible[DivisorSigma[1,#],EulerPhi[#]+9]&] (* _Harvey P. Dale_, May 24 2012 *)

%K nonn

%O 1,1

%A _Robert G. Wilson v_

%E a(9)-a(21) from _Donovan Johnson_, Feb 28 2012