A015806 Numbers k not congruent to 0 (mod 3) such that phi(k) + 4 | sigma(k).

175, 220, 350, 752, 3772, 4720, 5092, 15296, 80320, 269872, 632752, 807650, 1126672, 1304320, 4176896, 4386476, 20945920, 37030556, 1073463296, 17178755072, 34796530432, 85897707520, 274873450496

Offset

1,1

Comments

a(24) > 10^12. - Donovan Johnson, Feb 28 2012

Links

Table of n, a(n) for n=1..23.

Mathematica

Select[Range[100000],
Divisible[DivisorSigma[1, #], EulerPhi[#] + 4] && !
    Divisible[#, 3] &] (* David Nacin, Feb 28 2012 *)

Crossrefs

Sequence in context: A102538 A045145 A351720 * A369954 A109836 A332047

Adjacent sequences: A015803 A015804 A015805 * A015807 A015808 A015809

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Offset corrected and a(10)-a(23) from Donovan Johnson, Feb 28 2012

Status

approved