

A065800


Numbers n which, for some r, are rdigit maximizers of n/phi(n).


0



6, 30, 60, 90, 210, 420, 630, 840, 2310, 4620, 6930, 9240, 25410, 50820, 76230
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OFFSET

1,1


COMMENTS

I can show that for r > 1, the first rdigit term of the sequence is the smallest rdigit 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 rdigit terms are in arithmetic progression with common difference equal to the smallest rdigit term. For example, 210, 420, 630, 840 are in arithmetic progression with common difference 210. Obviously the rdigit minimizer of n/phi(n) is the largest prime of n digits.


LINKS

Table of n, a(n) for n=1..15.


EXAMPLE

30/phi(30) = 15/4 is maximal for twodigit numbers. 210/phi(210) = 35/8 is maximal for threedigit numbers.


CROSSREFS

Cf. A000010, A002110.
Sequence in context: A057229 A120734 A116360 * A181827 A263573 A145010
Adjacent sequences: A065797 A065798 A065799 * A065801 A065802 A065803


KEYWORD

nonn


AUTHOR

Joseph L. Pe, Dec 05 2001


STATUS

approved



