1,1
The next term, for k=149, has 126 digits.
Table of n, a(n) for n=1..3.
Select[(7^Range[200]-1)/6, PrimeQ]
Cf. A023000 ((7^n-1)/6), A004063 (n such that (7^n-1)/6 is prime).
Sequence in context: A292011 A306849 A022233 * A031551 A031731 A252048
Adjacent sequences: A102167 A102168 A102169 * A102171 A102172 A102173
nonn,bref
Roger L. Bagula, Mar 15 2005
approved
