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%I #24 Mar 16 2022 10:34:06
%S 1,2,3,6,26,190,610,2078,2670,7038,16466,89973,150374,157298,163367,
%T 419090,640627,879702,3479689,5618437,11304721,74106171,471591726,
%U 475915439,1198344149,2270643086,3051266010
%N Numbers k that divide Sum_{i=1..k} phi(i)^2, where phi(i) = totient function A000010.
%C Does a number k exist such that RootMeanSquare(phi(1), ..., phi(k)) is an integer?
%F {k: k | A057434(k)}. - _R. J. Mathar_, Sep 29 2008
%t lst = {}; s = 0; Do[ s = s + EulerPhi[n]^2; If[ Mod[s, n] == 0, AppendTo[lst, n]], {n, 10^9}]; lst (* _Robert G. Wilson v_, Oct 02 2008 *)
%o (PARI) s=0;for(n=1,1e6,s+=eulerphi(n)^2;if(s%n==0,print1(n", "))) \\ _Charles R Greathouse IV_, Mar 05 2013
%Y Cf. A000010, A057434, A048290, A140480.
%K nonn,more
%O 1,2
%A _Ctibor O. Zizka_, Sep 23 2008
%E a(8)-a(11) from _R. J. Mathar_, Sep 29 2008
%E a(12)-a(24) from _Robert G. Wilson v_, Oct 02 2008
%E a(25)-a(27) from _Donovan Johnson_, Aug 21 2011
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