A227049 Numbers n such that (15^n + 4^n)/19 is prime.

3, 31, 157, 239, 1553, 5521, 25561

Offset

1,1

Comments

All terms are primes.

a(8) > 10^5.

Links

Table of n, a(n) for n=1..7.

Mathematica

Select[ Prime[ Range[1, 100000] ], PrimeQ[ (15^# + 4^#)/19 ]& ]

Prog

(PARI) is(n)=ispseudoprime((15^n+4^n)/19) \\ Charles R Greathouse IV, Jun 06 2017

Crossrefs

Cf. A057181, A128071, A128342, A213176, A224501, A221637.

Sequence in context: A087389 A294394 A064055 * A078604 A195603 A089286

Adjacent sequences: A227046 A227047 A227048 * A227050 A227051 A227052

Keyword

hard,nonn,more

Author

Robert Price, Jun 29 2013

Status

approved