A055690 Numbers k such that 7^k == -1 (mod k-1).

2, 3, 5, 6, 9, 26, 45, 66, 87, 345, 765, 906, 3926, 8405, 11766, 23805, 35145, 42966, 59685, 95289, 317250, 413325, 416757, 722745, 770066, 890825, 938457, 1325826, 1921986, 3315378, 3675555, 5299250, 6791445, 6899685, 9371826, 10892313

Offset: 1

Author

Robert G. Wilson v, Jun 09 2000

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..285

Crossrefs

Cf. A055685, A055686, A055687, A055688, A055689, A055691, A055692, A055693, A055694, A055695.

Programs

Mathematica

Do[If[PowerMod[7, n, n-1]==n-2, Print[n]], {n, 2, 2*10^7}]