A337830 Odd integers k such that 6^((k-1)/2) + 1 == 0 (mod k*(k-1)/2).

2843, 2390123, 9893003, 16236347, 46353707, 334358459, 564092747, 584214107, 1640200619, 2010092603, 14044030043, 22315857803, 23753097803, 92758244699, 136542051227, 281195463179, 332945964107, 545960571227

Offset: 1

Author

Benoit Cloitre, Sep 24 2020

Keywords

• nonn
• more

Comments

Computed terms are prime.

Conjecture: a(n) == 1 mod 406 for n > 5. - Chai Wah Wu, Oct 07 2020

Crossrefs

Cf. A337818.

Programs

Mathematica

Select[Range[3, 10^7, 2], PowerMod[6, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* Amiram Eldar, Sep 24 2020 *)

Extensions

a(6)-a(13) from Amiram Eldar, Sep 24 2020

a(14)-a(15) from Bill McEachen, Jul 21 2025

a(16)-a(18) from Bill McEachen, Aug 03 2025