A337828 Odd integers k such that 3^((k-1)/2) + 1 == 0 (mod k*(k-1)/2).

5, 101, 62501, 1020101, 31562501, 139476101, 637562501, 789062501, 985502501, 2656262501, 7455062501, 19726562501, 53662562501

Offset

1,1

Comments

Computed terms are prime.

Links

Table of n, a(n) for n=1..13.

Mathematica

Select[Range[3, 3*10^7, 2], PowerMod[3, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* Amiram Eldar, Sep 24 2020 *)

Crossrefs

Cf. A337818.

Sequence in context: A113073 A349045 A337831 * A275749 A057207 A124986

Adjacent sequences: A337825 A337826 A337827 * A337829 A337830 A337831

Keyword

nonn,more

Author

Benoit Cloitre, Sep 24 2020

Extensions

a(7)-a(13) from Amiram Eldar, Sep 25 2020

Status

approved