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A231371
Squarefree composite numbers k such that 8 is a primitive root for all prime factors of k.
3
15, 33, 55, 87, 145, 159, 165, 177, 249, 265, 295, 303, 319, 321, 393, 415, 435, 447, 505, 519, 535, 537, 583, 591, 649, 655, 681, 745, 795, 807, 865, 879, 885, 895, 913, 951, 957, 985, 1041, 1111, 1135, 1167, 1177, 1245, 1257, 1329, 1345, 1383, 1401, 1441
OFFSET
1,1
COMMENTS
If k is the smallest integer satisfying 10^k == 1 (mod p), we say that 10 has order k (mod p). If n is the product of distinct primes p_i, the period of 1/n in base b is the least common multiple of the orders of b (mod p_i), provided b and n are relatively prime.
LINKS
Eric Weisstein's World of Mathematics, Primitive Root.
Wikipedia, Octal.
MATHEMATICA
q[n_] := CompositeQ[n] && SquareFreeQ[n] && AllTrue[FactorInteger[n][[;; , 1]], MultiplicativeOrder[8, #] == # - 1 &]; Select[Range[1441], q] (* Amiram Eldar, Oct 03 2021 *)
CROSSREFS
Subsequence of A024556.
Sequence in context: A071965 A242677 A020184 * A228318 A228321 A277385
KEYWORD
nonn
AUTHOR
STATUS
approved