A224691 Numbers n such that (13^n - 4^n)/9 is prime.

2, 5, 19, 109, 157, 8521, 26017, 26177

Offset

1,1

Comments

All terms are prime.

a(9) > 10^5.

Links

Table of n, a(n) for n=1..8.

Mathematica

Select[Prime[Range[1, 100000]], PrimeQ[(13^# - 4^#)/9]&]

Prog

(PARI) is(n)=ispseudoprime((13^n-4^n)/9) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A004063, A028491, A057468, A059801, A121877, A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032, A210506, A128347.

Sequence in context: A211207 A107882 A328977 * A192445 A089126 A113346

Adjacent sequences: A224688 A224689 A224690 * A224692 A224693 A224694

Keyword

nonn,hard,more

Author

Robert Price, Apr 15 2013

Status

approved