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A306451 Non-coprime pseudoprimes or primes to base 3: numbers k that are multiples of 3 and are such that k divides 3^k - 3. 2
3, 6, 66, 561, 726, 7107, 8205, 8646, 62745, 100101, 140097, 166521, 237381, 237945, 566805, 656601, 876129, 1053426, 1095186, 1194285, 1234806, 1590513, 1598871, 1938021, 2381259, 2518041, 3426081, 4125441, 5398401, 5454681, 5489121, 5720331, 5961441 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Union of {3} and (A122780 - {1} - A005935).
Numbers of the form 3*m such that 3^(3*m-1) == 1 (mod m).
The squarefree terms are listed in A306450.
LINKS
Jianing Song, Table of n, a(n) for n = 1..163 (all terms below 10^9)
FORMULA
66 is a term because 66 divides 3^66 - 3 = 3*(3^65 - 1) = 3*(3^5 - 1)*(3^60 + 3^55 + ... + 3^5 + 1) and 66 is divisible by 3.
PROG
(PARI) forstep(n=3, 1e7, 3, if(Mod(3, n)^n==3, print1(n, ", ")))
CROSSREFS
A258801 is a subsequence.
Sequence in context: A225789 A076551 A127637 * A068665 A229236 A050722
KEYWORD
nonn
AUTHOR
Jianing Song, Feb 17 2019
STATUS
approved

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Last modified June 16 11:53 EDT 2024. Contains 373429 sequences. (Running on oeis4.)