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A144857
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Numbers k that divide Sum_{i=1..k} phi(i)^2, where phi(i) = totient function A000010.
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1
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1, 2, 3, 6, 26, 190, 610, 2078, 2670, 7038, 16466, 89973, 150374, 157298, 163367, 419090, 640627, 879702, 3479689, 5618437, 11304721, 74106171, 471591726, 475915439, 1198344149, 2270643086, 3051266010
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OFFSET
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1,2
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COMMENTS
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Does a number k exist such that RootMeanSquare(phi(1), ..., phi(k)) is an integer?
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LINKS
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Table of n, a(n) for n=1..27.
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FORMULA
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{k: k | A057434(k)}. - R. J. Mathar, Sep 29 2008
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MATHEMATICA
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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 *)
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PROG
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(PARI) s=0; for(n=1, 1e6, s+=eulerphi(n)^2; if(s%n==0, print1(n", "))) \\ Charles R Greathouse IV, Mar 05 2013
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CROSSREFS
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Cf. A000010, A057434, A048290, A140480.
Sequence in context: A296259 A344935 A000341 * A090445 A228346 A269996
Adjacent sequences: A144854 A144855 A144856 * A144858 A144859 A144860
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KEYWORD
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nonn,more
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AUTHOR
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Ctibor O. Zizka, Sep 23 2008
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EXTENSIONS
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a(8)-a(11) from R. J. Mathar, Sep 29 2008
a(12)-a(24) from Robert G. Wilson v, Oct 02 2008
a(25)-a(27) from Donovan Johnson, Aug 21 2011
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STATUS
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approved
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