The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A293712 Numbers n such that psi(phi(n))/n > psi(phi(m))/m for all m < n, where phi is Euler's totient function (A000010) and psi is the Dedekind psi function (A001615). 0
 1, 5, 7, 13, 19, 31, 61, 151, 181, 211, 421, 631, 1051, 1471, 2311, 4621, 9241, 11551, 18481, 25411, 32341, 34651, 43891, 60653, 120121, 150151, 180181, 270271, 300301, 330331, 390391, 420421, 450451, 540541, 600601, 660661, 840841, 870871, 1023053, 2045003 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Sândor proved that lim sup psi(phi(n))/n = oo, hence this sequence is infinite. REFERENCES Jôzsef Sândor, On Dedekind’s arithmetical function, Seminarul de Teoria Structurilor, Univ. Timisoara, No. 51, 1988, pp. 1-15. LINKS Jôzsef Sândor, On the composition of some arithmetic functions, II, Journal of Inequalities in Pure and Applied Mathematics, Vol. 6, Issue 3, Article 73 (2005). MATHEMATICA psi[n_] := If[n < 1, 0, n*Sum[MoebiusMu[d]^2/d, {d, Divisors@n}]]; a={}; rm=0; Do[r=psi[EulerPhi[n]]/n; If[r>rm, rm=r; AppendTo[a, n]], {n, 1, 100000}]; a CROSSREFS Cf. A000010, A001615. Sequence in context: A006512 A074304 A264865 * A297674 A072677 A117249 Adjacent sequences:  A293709 A293710 A293711 * A293713 A293714 A293715 KEYWORD nonn AUTHOR Amiram Eldar, Oct 15 2017 STATUS approved

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

Last modified April 18 04:49 EDT 2021. Contains 343072 sequences. (Running on oeis4.)