A178996 Numbers n such that 5^n mod 2^n is prime.

3, 10, 19, 24, 28, 61, 79, 96, 104, 125, 132, 191, 196, 243, 292, 302, 462, 466, 586, 621, 1508, 3307, 3823, 4729, 5370, 6721, 8110, 11145, 13502, 13762, 20266, 27868, 38522, 75470

Offset

1,1

Comments

Here 'mod' denotes the binary modulo operation (nonnegative remainder).

Links

Table of n, a(n) for n=1..34.

Mathematica

fQ[n_] := PrimeQ@ PowerMod[5, n, 2^n]; k = 1; lst = {}; While[k < 17501, If[fQ@ k, AppendTo[lst, k]]; k++]; lst

Prog

(PARI) for(n=1, 9999, ispseudoprime(5^n % 2^n) &  print1(n", ")) \\ M. F. Hasler, Jan 03 2011
(PARI) for(n=1, 1e5, if(ispseudoprime(lift(Mod(5, 2^n)^n)), print1(n", "))) \\ Charles R Greathouse IV, Oct 10 2011

Crossrefs

Cf. A178995.

Sequence in context: A265487 A074893 A074178 * A127852 A064027 A321543

Adjacent sequences: A178993 A178994 A178995 * A178997 A178998 A178999

Keyword

nonn,hard

Author

Robert G. Wilson v, Jan 03 2011

Extensions

a(31)-a(34) from Charles R Greathouse IV, Oct 10 2011

Status

approved