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A074920
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Integers k such that phi(k) = 6k/Pi^2 rounded to nearest integer.
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2
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1, 2, 3, 4, 33, 39, 99, 3237, 9711, 2069301, 6207903, 45502509, 24091595067
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OFFSET
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1,2
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COMMENTS
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The average value of phi(n) can be approximated for large n by 6n/Pi^2 (Tattersall, p. 162).
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REFERENCES
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James J. Tattersall, "Elementary Number Theory in Nine Chapters", Cambridge University Press, 2001.
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LINKS
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EXAMPLE
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phi(99) = 60 and 6*99/Pi^2 = 60.1848...., which rounds off to 60. Hence 99 is a term of the sequence.
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MATHEMATICA
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s = Pi^2; l = {}; Do[ If[Abs[EulerPhi[n] - 6 n/ s] <= 0.5, l = Append[l, n]], {n, 1, 10^5}]; l
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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