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A066167
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Numbers n such that phi(n) = (phi(n+1) + phi(n-1))/2.
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2
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5187, 5313, 273525, 292005, 494715, 536055, 657855, 2379975, 3045075, 9960045, 15091545, 19420665, 23977305, 28292745, 45864225, 62361495, 81758325, 93794715, 213205575, 309227655, 602444325, 806687427, 1375738845, 1411639047, 1538174925, 1589814975, 1628145057
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OFFSET
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1,1
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COMMENTS
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Identical to the sequence of n such that phi(n-1), phi(n), phi(n+1) are in arithmetic progression.
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LINKS
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EXAMPLE
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Phi(5313) = 2640 = (2656 + 2624)/2 = (phi(5314) + phi(5212))/2.
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MATHEMATICA
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Select[ Range[ 2, 10^6 ], EulerPhi[ # ] == (EulerPhi[ #+1 ] + EulerPhi[ #-1 ])/2 & ]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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