OFFSET
0,1
COMMENTS
Conjecture: a(n) > 0 for all n. That is to say, every number occurs in A328412.
It seems that most terms are congruent to 2 modulo 4.
LINKS
EXAMPLE
(Z/mZ)* = C_2 X C_42 has exactly 6 solutions m = 129, 147, 172, 196, 258, 294; for any k < 21, (Z/mZ)* = C_2 X C_(2k) has either fewer than or more than 6 solutions, so a(6) = 21.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Jianing Song, Oct 14 2019
STATUS
approved