The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A355667 Least number phi(k) such that n * phi(k) < k, where phi is Euler's totient function. 1
 1, 2, 8, 48, 5760, 36495360, 1854081073152000, 400440702414394285778534400000, 165062110921422523175104166476600499887194872217600000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is the Euler totient of A091456(n). Useful for calculating a simple upper bound of the inverse phi function. LINKS Nico Mexis, Table of n, a(n) for n = 1..13 John Abbott and Nico Mexis, Cyclotomic Factors and LRS-Degeneracy, arXiv:2403.08751 [math.AC], 2024. See pp. 9, 24. FORMULA a(n) = A000010(A091456(n)). a(n) = A000010(A091439(n+1)). EXAMPLE If we know n=276, then all numbers k with phi(k)=n will satisfy k < 5*n since m=a(5) is the first number in the sequence with n < m. MATHEMATICA a[n_] := Module[{k = 1, p = 1, e}, While[k <= n*(e = EulerPhi[k]), p = NextPrime[p]; k *= p]; e]; Array[a, 9] (* Amiram Eldar, Jul 13 2022 *) PROG (PARI) a(n)=my(k=1); forprime(p=2, , if(n*eulerphi(k)

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 19 05:57 EDT 2024. Contains 373492 sequences. (Running on oeis4.)