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
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
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Jianing Song, Oct 14 2019
STATUS
approved