A015732 Even numbers k such that d(k) | phi(k).

8, 10, 18, 24, 26, 28, 30, 34, 40, 52, 56, 58, 70, 72, 74, 76, 78, 82, 84, 88, 90, 98, 102, 104, 106, 108, 110, 120, 122, 124, 126, 128, 130, 136, 140, 146, 148, 152, 156, 168, 170, 172, 174, 176, 178, 182, 184, 190, 194, 198, 202, 210, 218, 222, 224, 226, 228

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A020491.

Cf. A000005 (d), A000010 (phi).

Programs

Mathematica

Select[Range[0, 250, 2], Divisible[EulerPhi[#], DivisorSigma[0, #]] &] (* Amiram Eldar, Dec 05 2024 *)

PARI

is(k) = if(k % 2, 0, my(f = factor(k)); !(eulerphi(f) % numdiv(f))); \\ Amiram Eldar, Dec 05 2024