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A337831
Odd integers k such that 7^((k-1)/2) + 1 == 0 (mod k*(k-1)/2).
0
5, 101, 62501, 1020101, 3512501, 12650501, 22598021, 31562501, 365328101, 789062501, 11412000101, 64014060101
OFFSET
1,1
COMMENTS
Computed terms are prime.
MATHEMATICA
Select[Range[3, 10^7, 2], PowerMod[7, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* Amiram Eldar, Sep 24 2020 *)
CROSSREFS
Cf. A337818.
Sequence in context: A009765 A113073 A349045 * A337828 A275749 A057207
KEYWORD
nonn,more
AUTHOR
Benoit Cloitre, Sep 24 2020
EXTENSIONS
a(9)-a(12) from Amiram Eldar, Sep 25 2020
STATUS
approved