A180061 Numbers k such that (2^(2^k mod k) mod k) = 4.

5, 6, 7, 9, 11, 12, 13, 17, 19, 21, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 63, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 121, 127, 131, 133, 137, 139, 149, 151, 157, 163, 167, 172, 173, 179, 181, 190, 191, 193, 196, 197, 199, 211

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 14 2011

Keywords

• nonn

Comments

The composite terms in this sequence start 6, 9, 12, 21, 63, 121, 133, 172, 190, 196, ... - R. J. Mathar, Jan 14 2011

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000040, A000079, A179976, A180060.

Programs

Mathematica

Select[Range[300],PowerMod[2,PowerMod[2,#,#],#]==4&] (* Harvey P. Dale, Sep 08 2016 *)

PARI

s=[]; for(n=1, 1000, if((2^(2^n%n)%n)==4, s=concat(s, n))); s \\ Colin Barker, Jun 27 2014

Formula

A180060(a(n)) = 4.

Extensions

Terms corrected by R. J. Mathar, Jan 14 2011