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Search: id:A083545
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| A083545 |
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Geometric mean of Euler-phi of 2 consecutive integers {n,n+1} is also an integer: n's are collected here. |
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+0
2
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| 1, 3, 15, 19, 95, 104, 125, 164, 194, 255, 259, 341, 491, 495, 504, 512, 513, 584, 591, 629, 679, 755, 775, 975, 1024, 1147, 1247, 1254, 1260, 1313, 1358, 1463, 1469, 1538, 1615, 1728, 1919, 1962, 1970, 2047, 2071, 2090, 2204, 2299, 2321, 2345, 2404, 2625
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(m)=x is such that Sqrt(A000010[x]*A000010[x+1]) is integer. Values of x solutions to phi[x+1].phi[x]=A083542[x]=y^2,
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EXAMPLE
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x=19: phi[19]=18,phi[20]=8, 8.18=144-12.12, so 19 is here.
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MATHEMATICA
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f[x_] := EulerPhi[x]; Do[s=Sqrt[f[n+1]*f[n]]; If[IntegerQ[s], Print[n]], {n, 1, 5000}]
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CROSSREFS
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Cf. A000010, A083542, A083542, A066813, A058515, A083538, A083546.
Sequence in context: A032644 A124877 A111517 this_sequence A097571 A048087 A001897
Adjacent sequences: A083542 A083543 A083544 this_sequence A083546 A083547 A083548
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), May 21 2003
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