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 A066763 Numbers n such that (n, phi(n)) lies on a circle with integral radius centered at the origin, i.e., n^2 + phi(n)^2 is a square. 1
 15, 45, 70, 75, 135, 140, 225, 280, 350, 375, 377, 405, 490, 560, 627, 665, 675, 700, 980, 1120, 1125, 1215, 1400, 1750, 1875, 1881, 1960, 2025, 2240, 2450, 2800, 3325, 3375, 3430, 3500, 3645, 3655, 3920, 4480, 4655, 4900, 4901, 5600, 5625, 5643, 6075 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Harry J. Smith, Table of n, a(n) for n = 1..1000 EXAMPLE 15^2 + phi(15)^2 = 225 + 64 = 289 = 17^2, so 15 is a term of the sequence. MATHEMATICA Select[ Range[ 1, 10^4 ], IntegerQ[ Sqrt[ #^2 + EulerPhi[ # ]^2 ] ] & ] PROG (PARI) { n=0; for (m=1, 10^10, if (issquare(m^2 + eulerphi(m)^2), write("b066763.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Mar 23 2010 CROSSREFS Sequence in context: A293625 A084821 A298462 * A164788 A033849 A194715 Adjacent sequences:  A066760 A066761 A066762 * A066764 A066765 A066766 KEYWORD nonn AUTHOR Joseph L. Pe, Jan 17 2002 STATUS approved

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Last modified April 19 00:03 EDT 2021. Contains 343098 sequences. (Running on oeis4.)