login
A272593
Numbers n such that the multiplicative group modulo n is the direct product of 3 cyclic groups.
9
24, 40, 48, 56, 60, 72, 80, 84, 88, 96, 104, 105, 112, 132, 136, 140, 144, 152, 156, 160, 165, 176, 180, 184, 192, 195, 200, 204, 208, 210, 216, 220, 224, 228, 231, 232, 248, 252, 255, 260, 272, 273, 276, 285, 288, 296, 300, 304, 308, 315, 320, 328, 330, 340, 344, 345, 348, 352, 357, 364, 368, 372, 376, 380
OFFSET
1,1
COMMENTS
Numbers n such that A046072(n) = 3.
MATHEMATICA
A046072[n_] := Which[n == 1 || n == 2, 1,
OddQ[n], PrimeNu[n],
EvenQ[n] && !Divisible[n, 4], PrimeNu[n] - 1,
Divisible[n, 4] && !Divisible[n, 8], PrimeNu[n],
Divisible[n, 8], PrimeNu[n] + 1];
Select[Range[400], A046072[#] == 3&] (* Jean-François Alcover, Dec 22 2021, after Geoffrey Critzer in A046072 *)
PROG
(PARI) for(n=1, 10^3, my(t=#(znstar(n)[2])); if(t==3, print1(n, ", ")));
CROSSREFS
Cf. A046072.
Direct product of k groups: A033948 (k=1), A272592 (k=2), A272594 (k=4), A272595 (k=5), A272596 (k=6), A272597 (k=7), A272598 (k=8), A272599 (k=9).
Sequence in context: A271422 A362148 A062374 * A048104 A334801 A362594
KEYWORD
nonn
AUTHOR
Joerg Arndt, May 05 2016
STATUS
approved