A091456 Least number k such that n * phi(k) < k, where phi is Euler's totient function.

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

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