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A091456
Least number k such that n * phi(k) < k, where phi is Euler's totient function.
4
2, 6, 30, 210, 30030, 223092870, 13082761331670030, 3217644767340672907899084554130, 1492182350939279320058875736615841068547583863326864530410
OFFSET
1,1
COMMENTS
By Mertens' theorem and the Prime Number Theorem log log a(n) ~ n / e^gamma. - Charles R Greathouse IV, Sep 07 2012
PROG
(PARI) a(n) = {k = 1; while (n*eulerphi(k) >= k, k++); k; } \\ Michel Marcus, Sep 25 2013
(PARI) a(n)=my(k=1); forprime(p=2, , if(n*eulerphi(k)<k, return(k), k*=p)) \\ Charles R Greathouse IV, Sep 25 2013
CROSSREFS
Subsequence of A002110. Cf. A000010, A054741, A073087, A091439 (n * phi(k) <= k).
Sequence in context: A077176 A101178 A294925 * A354411 A293756 A161620
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Jan 10 2004
STATUS
approved