A015733 Numbers k such that d(k) does not divide phi(k).

2, 4, 6, 12, 14, 16, 20, 22, 25, 27, 32, 36, 38, 42, 44, 46, 48, 50, 54, 60, 62, 64, 66, 68, 75, 80, 81, 86, 92, 94, 96, 100, 112, 114, 116, 118, 121, 132, 134, 138, 142, 144, 150, 154, 158, 160, 162, 164, 166, 180, 186, 188, 189, 192, 196, 200, 204

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..18157 (first 2000 terms from Enrique Pérez Herrero)

Crossrefs

Cf. A000005 (d), A000010 (phi), A015734, A020491 (d(k) does divide phi(k)).

Programs

Mathematica

Select[Range[204], ! Divisible[EulerPhi[#], DivisorSigma[0, #]] &]

PARI

is(k) = {my(f = factor(k), d = numdiv(f), p = eulerphi(f)); p % d;} \\ Amiram Eldar, May 15 2024