A273601 Numbers k such that (11^k - 9^k)/2 is prime.

5, 31, 271, 929, 2789, 4153

Offset: 1

Author

Tim Johannes Ohrtmann, May 26 2016

Keywords

• nonn
• more
• hard

Comments

All terms are prime.

The corresponding primes: 51001, 95780952266636767336259095696501, ...

a(7) > 50000. - Michael S. Branicky, Nov 11 2024

Crossrefs

Cf. A005808, A210506, A128027, A216181, A128347, A273598, A273599, A273600, A062577.

Programs

Mathematica

Select[Range[1, 10000], PrimeQ[(11^# - 9^#)/2] &]

PARI

for(n=1, 10000, if(isprime((11^n - 9^n)/2), print1(n, ", ")))