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%I #24 Feb 14 2021 13:00:11
%S 1,3,5,25,125,625,3125,15625,78125,390625,1953125,9765625,48828125,
%T 244140625,1220703125,6103515625,30517578125,152587890625,
%U 762939453125,3814697265625,19073486328125,95367431640625,476837158203125,2384185791015625,11920928955078125,59604644775390625,298023223876953125
%N Numbers k such that k = Sum_{d|phi(k)} mu(phi(d))*phi(k)/d.
%C Does sequence consist of 1,3 and all powers of 5? Answer from _Lambert Klasen_, Oct 07 2005: Yes! See attached file.
%H Lambert Klasen, <a href="/A074701/a074701.txt">Notes on A074701</a>
%p with(numtheory): a:=proc(n) local div: div:=convert(divisors(phi(n)),list): if add(mobius(phi(div[j]))*phi(n)/div[j],j=1..nops(div))=n then n else fi end: seq(a(n),n=1..5000); # _Emeric Deutsch_, Mar 27 2005
%o (PARI) isok(n) = n == sumdiv(eulerphi(n), d, moebius(eulerphi(d))*eulerphi(n)/d); \\ _Michel Marcus_, Aug 15 2019
%Y Cf. A000351. [_R. J. Mathar_, Sep 23 2008]
%K nonn
%O 1,2
%A _Benoit Cloitre_, Sep 03 2002
%E 2 more terms from _Emeric Deutsch_, Mar 27 2005
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