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Search: id:A065800
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| A065800 |
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Numbers n which, for some r, are r-digit maximizers of n/EulerPhi(n). |
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+0
1
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| 6, 30, 60, 90, 210, 420, 630, 840, 2310, 4620, 6930, 9240, 25410, 50820, 76230
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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I can show that for r > 1, the first r-digit term of the sequence is the smallest r-digit primorial, if it exists. It remains to investigate the first terms when existence fails. It is also not hard to see that for r > 1, the r-digit terms are in arithmetic progression with common difference equal to the smallest r-digit term. For example, 210, 420, 630, 840 are in arithmetic progression with common difference 210. Obviously the r-digit minimizer of n/EulerPhi(n) is the largest prime of n digits.
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EXAMPLE
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30/EulerPhi(30) = 15/4 is maximal for two-digit numbers. 210/EulerPhi(210) = 35/8 is maximal for three-digit numbers.
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CROSSREFS
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Cf. A000010, A002110.
Sequence in context: A057229 A120734 A116360 this_sequence A145010 A056835 A056836
Adjacent sequences: A065797 A065798 A065799 this_sequence A065801 A065802 A065803
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Dec 05 2001
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