OFFSET
2,1
COMMENTS
All terms are odd primes.
a(49) > 143800. - Robert Price, Mar 29 2019
LINKS
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
Eric Weisstein's World of Mathematics, Repunit.
FORMULA
a(n) = A084742(2n-1).
MATHEMATICA
A126659[n_] := Module[{k = 1}, If[n == 14, Return[0]]; While[! PrimeQ[((2 n - 1)^k + 1)/(2 n)], k++]; k]; Table[A126659[n], {n, 2, 48}] (* Robert Price, Oct 29 2018 *)
PROG
(PARI) a(n) = {if (n==14, return(0)); my(k=3); while (! isprime(((2*n-1)^k + 1)/(2*n)), k = nextprime(k+1)); k; } \\ Michel Marcus, Nov 23 2018
CROSSREFS
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 09 2007, Feb 10 2007
STATUS
approved