The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A143423 Least even number k such that phi(k) = n, where n runs through the values (A002202) taken by phi. 1
 2, 4, 8, 14, 16, 22, 26, 32, 38, 44, 46, 52, 58, 62, 64, 74, 82, 86, 92, 94, 104, 106, 162, 116, 118, 122, 128, 134, 142, 146, 158, 164, 166, 172, 178, 188, 194, 202, 206, 212, 214, 218, 242, 226, 236, 244, 254, 256, 262, 268, 274, 278, 284, 292, 298, 302, 314 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Such an even number always exists. LINKS T. D. Noe, Table of n, a(n) for n=1..10000 Maxim Rytin, Finding the Inverse of Euler Totient Function (1999). MAPLE f:= proc(m) local L; L:= numtheory:-invphi(m); if L = [] then NULL else min(select(type, L, even)) fi end proc: map(f, [1, seq(2*k, k=1..1000)]); # Robert Israel, Oct 07 2015 MATHEMATICA f[m_] := Module[{L}, L = invphi[m]; If[L == {}, Nothing, Min[Select[L, EvenQ]]]]; f /@ Join [{1}, 2 Range[1000]] (* Jean-François Alcover, Aug 28 2020, using Maxim Rytin's invphi function *) CROSSREFS Cf. A002181 (least k such that phi(k)=n), A006511 (largest k such that phi(k)=n). Sequence in context: A086303 A209838 A121982 * A253142 A069049 A124853 Adjacent sequences: A143420 A143421 A143422 * A143424 A143425 A143426 KEYWORD nonn AUTHOR T. D. Noe, Aug 14 2008 STATUS approved

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 19:59 EDT 2024. Contains 373507 sequences. (Running on oeis4.)