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!)
 A328417 Numbers k such that A328412(k) sets a new record; numbers k such that (Z/mZ)* = C_2 X C_(2k) has more solutions for m than all k' < k, where (Z/mZ)* is the multiplicative group of integers modulo m. 2
 1, 2, 6, 30, 78, 210, 690, 1050, 4830 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Conjecture: this sequence is infinite. That is to say, A328412 is unbounded. It seems that a(n) == 2 (mod 4) for n > 1. LINKS Wikipedia, Multiplicative group of integers modulo n EXAMPLE For k = 30: (Z/mZ)* = C_2 X C_60 has 11 solutions, namely m = 143, 155, 175, 183, 225, 244, 286, 310, 350, 366, 450; for all k' < 30, (Z/mZ)* = C_2 X C_(2k') has fewer than 11 solutions. So 30 is a term. PROG (PARI) my(t=0); for(k=1, 5000, if(A328412(k)>t, print1(k, ", "); t=A328412(k))) \\ See A328412 for its program CROSSREFS Cf. A328412, A328418. Sequence in context: A211889 A174276 A117849 * A290760 A088857 A099081 Adjacent sequences:  A328414 A328415 A328416 * A328418 A328419 A328420 KEYWORD nonn,hard,more AUTHOR Jianing Song, Oct 14 2019 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 August 10 22:22 EDT 2020. Contains 336403 sequences. (Running on oeis4.)