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A066763
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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.
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2
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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
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OFFSET
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1,1
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LINKS
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EXAMPLE
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15^2 + phi(15)^2 = 225 + 64 = 289 = 17^2, so 15 is a term of the sequence.
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MATHEMATICA
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Select[ Range[ 1, 10^4 ], IntegerQ[ Sqrt[ #^2 + EulerPhi[ # ]^2 ] ] & ]
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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