A273814 Numbers k such that (12^k - 7^k)/5 is prime.

2, 3, 7, 13, 47, 89, 139, 523, 1051

Offset

1,1

Comments

All terms are prime.

The corresponding primes are 19, 277, 7001653, 21379263273733, 105329145253605843602014309589572596276217801876213, ...

Links

Table of n, a(n) for n=1..9.

Maple

A273814:=n->`if`(isprime((12^n - 7^n)/5), n, NULL): seq(A273814(n), n=1..10^3); # Wesley Ivan Hurt, Jun 01 2016

Mathematica

Select[Range[1, 10000], PrimeQ[(12^# - 7^#)/5] &]

Prog

(PARI) for(n=1, 10000, if(isprime((12^n - 7^n)/5), print1(n, ", ")))

Crossrefs

Cf. A004064, A062578, A128348.

Sequence in context: A349327 A166945 A257393 * A371131 A361988 A085872

Adjacent sequences: A273811 A273812 A273813 * A273815 A273816 A273817

Keyword

nonn,more,hard

Author

Tim Johannes Ohrtmann, May 31 2016

Status

approved