A102170 Primes of the form (7^k-1)/6.

2801, 16148168401, 85053461164796801949539541639542805770666392330682673302530819774105141531698707146930307290253537320447270457

Offset: 1

Author

Roger L. Bagula, Mar 15 2005

Keywords

• nonn
• hard

Comments

The next term, for k=149, has 126 digits.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..4

Crossrefs

Cf. A023000 ((7^n-1)/6), A004063 (k such that (7^k-1)/6 is prime).

Programs

Mathematica

Select[(7^Range[200]-1)/6, PrimeQ]

Formula

a(n) = A023000(A004063(n)). - Amiram Eldar, Jun 04 2025