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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 (list; graph; refs; listen; history; text; internal format)
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

LINKS

Table of n, a(n) for n=1..9.

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

Adjacent sequences: A091453 A091454 A091455 * A091457 A091458 A091459

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Jan 10 2004

STATUS

approved

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Last modified February 1 12:28 EST 2023. Contains 359993 sequences. (Running on oeis4.)