A068535 Numbers k such that 2^k mod k = 2^k mod k^2.

1, 2, 4, 8, 16, 32, 35, 64, 128, 256, 297, 512, 1024, 1093, 2048, 2186, 2590, 3279, 3511, 4096, 4372, 5465, 6558, 7022, 7651, 8192, 8744, 9837, 10533, 10930, 13116, 14044, 14209, 16384, 21066, 23175, 24012, 24577, 26592, 28088, 31599, 32768, 35110, 38621, 42132

Offset: 1

Author

Benoit Cloitre, Mar 22 2002

Keywords

• easy
• nonn

Comments

Sequence contains all numbers of the form 2^k (A000079) but also many others as the subsequence of primes in A001220.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..72

Crossrefs

Cf. A000079, A001220, A125773, A125774, A125775.

Programs

Mathematica

Select[Range[33000],PowerMod[2,#,#]==PowerMod[2,#,#^2]&] (* Harvey P. Dale, Oct 29 2017 *)

Extensions

More terms from Amiram Eldar, Jun 19 2022