A176817 Nonprimes k such that 2^(k-1) == 4^(k-1) (mod k).

1, 4, 8, 16, 28, 32, 64, 112, 128, 256, 341, 448, 496, 512, 561, 645, 1016, 1024, 1105, 1288, 1387, 1729, 1792, 1905, 2044, 2047, 2048, 2416, 2465, 2701, 2821, 3277, 4033, 4096, 4369, 4371, 4672, 4681, 4984, 5461, 6601, 7168, 7936, 7957, 8128, 8192, 8321, 8481, 8911

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 07 2010

Keywords

• nonn

Comments

All powers of two are present.

Crossrefs

Cf. A062173, A062175, A176176.

Programs

Mathematica

 fQ[n_] := !PrimeQ@ n && PowerMod[2, n - 1, n] == PowerMod[4, n - 1, n]; Select[ Range@ 10000, fQ]