A244723 Nonprimes n such that, mu(n) = mu(phi(n)).

1, 8, 12, 14, 16, 20, 22, 24, 25, 27, 28, 32, 36, 40, 44, 45, 46, 48, 50, 52, 54, 56, 60, 63, 64, 68, 72, 75, 76, 80, 81, 84, 88, 90, 92, 94, 96, 99, 100, 104, 108, 112, 116, 117, 118, 120, 124, 125, 126, 128, 132, 135, 136, 140, 144, 147, 148, 150, 152, 153, 156, 160, 162, 164, 166

Offset: 1

Author

Torlach Rush, Jul 04 2014

Keywords

• nonn
• easy

Comments

Odd terms, with the exception of 1, are not squarefree. - Torlach Rush, Jul 22 2014.

2*p, where p is an odd prime, is in the sequence iff p is in A088179. - Robert Israel, Jul 31 2014

Links

• Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A078330, A000010, A008683, A053850, A088179.

Programs

Maple

filter:= proc(n) uses numtheory;  not(isprime(n)) and mobius(n) = mobius(phi(n)) end proc;
select(filter, [$1..1000]); # Robert Israel, Jul 31 2014

Mathematica

searchMax = 200; Complement[Select[Range[searchMax], MoebiusMu[#] == MoebiusMu[EulerPhi[#]] &], Prime[Range[PrimePi[searchMax]]]] (* Alonso del Arte, Jul 05 2014 *)
Select[Range[searchMax], !PrimeQ[#] && MoebiusMu[#] == MoebiusMu[EulerPhi[#]]& ] (* Zak Seidov, Jul 31 2014 *)

PARI

for(n=1,10^3,if(!isprime(n)&&moebius(eulerphi(n))==moebius(n),print1(n,", "))) \\ Derek Orr, Jul 30 2014