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Primes of the form (7^k-1)/6.
4

%I #7 Mar 30 2012 17:34:14

%S 2801,16148168401,

%T 85053461164796801949539541639542805770666392330682673302530819774105141531698707146930307290253537320447270457

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

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

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

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

%K nonn,bref

%O 1,1

%A _Roger L. Bagula_, Mar 15 2005