The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A144857 Numbers k that divide Sum_{i=1..k} phi(i)^2, where phi(i) = totient function A000010. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Does a number k exist such that RootMeanSquare(phi(1), ..., phi(k)) is an integer? LINKS FORMULA {k: k | A057434(k)}. - R. J. Mathar, Sep 29 2008 MATHEMATICA 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 *) PROG (PARI) s=0; for(n=1, 1e6, s+=eulerphi(n)^2; if(s%n==0, print1(n", "))) \\ Charles R Greathouse IV, Mar 05 2013 CROSSREFS Cf. A000010, A057434, A048290, A140480. Sequence in context: A296259 A344935 A000341 * A090445 A228346 A269996 Adjacent sequences:  A144854 A144855 A144856 * A144858 A144859 A144860 KEYWORD nonn,more AUTHOR Ctibor O. Zizka, Sep 23 2008 EXTENSIONS 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 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 27 19:31 EDT 2022. Contains 354898 sequences. (Running on oeis4.)