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A329095
Odd numbers k such that x^2 == 2 (mod k) has no solution.
2
3, 5, 9, 11, 13, 15, 19, 21, 25, 27, 29, 33, 35, 37, 39, 43, 45, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 75, 77, 81, 83, 85, 87, 91, 93, 95, 99, 101, 105, 107, 109, 111, 115, 117, 121, 123, 125, 129, 131, 133, 135, 139, 141, 143, 145, 147, 149, 153, 155, 157, 159, 163
OFFSET
1,1
COMMENTS
Complement of A058529 over the odd numbers: odd numbers k such that x^2 == 2 (mod k) has solutions.
Odd numbers k such that at least one prime factor of k is congruent to 3 or 5 modulo 8 (at least one prime factor is in A003629).
Also odd terms in A025020.
LINKS
EXAMPLE
x^2 == 2 (mod 45) has no solution, so 45 is a term.
MAPLE
filter:= proc(t) (numtheory:-factorset(t) mod 8) intersect {3, 5} <> {} end proc:
select(filter, [seq(i, i=1..1000, 2)]); # Robert Israel, Nov 05 2019
MATHEMATICA
Reap[Do[If[AnyTrue[FactorInteger[k][[All, 1]], MatchQ[Mod[#, 8], 3|5]&], Sow[k]], {k, 1, 999, 2}]][[2, 1]] (* Jean-François Alcover, Aug 22 2020 *)
PROG
(PARI) isA329095(k) = (k%2) && !issquare(Mod(2, k))
CROSSREFS
Cf. A003629. A047621 is a subsequence.
Cf. A058529, A057126, A025020 (numbers k such that x^2 == 2 (mod k) has no solution).
Sequence in context: A368603 A173263 A285141 * A319009 A294427 A141231
KEYWORD
nonn,easy
AUTHOR
Jianing Song, Nov 04 2019
STATUS
approved