A113916 Numbers n such that (p^n-1)/(p-1) is prime where p is the n-th prime.

3, 7, 19, 31, 307, 421

Offset

1,1

Comments

Note that n must itself be a prime.

Links

Table of n, a(n) for n=1..6.

Mathematica

Do[ p = Prime[n]; If[PrimeQ[(p^n - 1)/(p - 1)], Print[n]], {n, 1800}] (* Robert G. Wilson v *)

Crossrefs

Sequence in context: A102271 A145039 A112633 * A227502 A268065 A049490

Adjacent sequences: A113913 A113914 A113915 * A113917 A113918 A113919

Keyword

nonn

Author

Joao da Silva (zxawyh66(AT)yahoo.com), Jan 30 2006

Status

approved