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

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

Offset: 1

Author

Tim Johannes Ohrtmann, May 31 2016

Keywords

• nonn
• more
• hard

Comments

All terms are prime.

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

a(10) > 50000. - Michael S. Branicky, Nov 12 2024

Crossrefs

Cf. A004064, A062578, A128348.

Programs

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] &]

PARI

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