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%I #45 Aug 11 2014 23:18:46
%S 1,9,14,18,22,46,94,118,166,214,334,358,422,454,526,662,694,718,766,
%T 926,934,958,961,1006,1094,1126,1142,1174,1382,1438,1678,1718,1726,
%U 1774,1822,1849,1922,1934,1966,2038,2246,2374,2462,2566,2582,2606,2614,2638,2654,2734,2878,2966,2974,3046
%N Nonprimes n such that mu(phi(n)) = 1.
%C Odd terms > 1 are the square of some prime: a(2) = 9 = 3^2, a(23) = 961 = 31^2, a(36) = 1849 = 43^2, ... .
%C Odd terms > 1 are A078330^2. Even terms are 2*A088179 and 2*A078330^2. - _Robert Israel_, Aug 01 2014
%H Michael De Vlieger, <a href="/A244466/b244466.txt">Table of n, a(n) for n = 1..11320</a>
%e 9 is not prime, phi(9) = 6 and mu(6) = 1, mu(phi(9)) = 1, so 9 is here.
%p filter:= n -> not isprime(n) and numtheory:-mobius(numtheory:-phi(n))=1:
%p select(filter, [$1..10000]); # _Robert Israel_, Aug 01 2014
%t Select[Range[3200],
%t And[MoebiusMu[EulerPhi[#]] == 1,
%t Not[PrimeQ[#]]] &] (* _Michael De Vlieger_, Aug 06 2014 *)
%o (C) a(n) {return mu(phi(n))==1 ? n : ;}
%o (PARI) for(n=1,10^4,if(moebius(eulerphi(n))==1,print1(n,", "))) \\ _Derek Orr_, Aug 01 2014
%o (Python)
%o from sympy import totient,factorint,primefactors,isprime
%o [n for n in range(1,10**5) if n == 1 or (not isprime(n) and max(factorint(totient(n)).values()) < 2 and (-1)**len(primefactors(totient(n))) == 1)] # _Chai Wah Wu_, Aug 06 2014
%Y Cf. A078330, A088179.
%K nonn,easy
%O 1,2
%A _Torlach Rush_, Jun 28 2014
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