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%I #43 Jun 18 2022 04:06:47
%S 1,1,2,2,2,2,6,2,6,2,10,2,6,6,2,2,2,6,6,2,6,10,22,2,10,6,6,6,14,2,30,
%T 2,10,2,6,6,6,6,6,2,10,6,42,10,6,22,46,2,42,10,2,6,26,6,10,6,6,14,58,
%U 2,30,30,6,2,6,10,66,2,22,6,70,6,6,6,10,6,30,6,78,2,6,10,82,6,2,42,14,10,22
%N Largest squarefree number dividing phi(n).
%C Also largest squarefree number dividing Carmichael's lambda, A002322(n). - _Antti Karttunen_, Jul 17 2017
%H Antti Karttunen, <a href="/A080400/b080400.txt">Table of n, a(n) for n = 1..16384</a>
%F a(n) = A007947(A000010(n)).
%F a(m * n) = A007947(a(m) * a(n)) if gcd(m, n) = 1. - _David A. Corneth_, Jul 16 2017
%F a(n) = A007947(A002322(n)). - _Antti Karttunen_, Jul 17 2017
%t Table[Max[Select[Divisors[EulerPhi[n]],SquareFreeQ]],{n,90}] (* _Harvey P. Dale_, Jul 05 2012 *)
%t a[n_] := Times @@ FactorInteger[EulerPhi[n]][[;; , 1]]; Array[a, 100] (* _Amiram Eldar_, Jun 18 2022 *)
%o (PARI) A080400(n) = factorback(factorint(eulerphi(n))[, 1]); \\ _Antti Karttunen_ & _David A. Corneth_, Jul 16 2017
%Y Cf. A000010, A002322, A007947, A034380, A289624.
%K nonn
%O 1,3
%A _Labos Elemer_, Mar 19 2003
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