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A113916 Numbers n such that (p^n-1)/(p-1) is prime where p is the n-th prime. 0
3, 7, 19, 31, 307, 421 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 22 04:39 EDT 2019. Contains 322329 sequences. (Running on oeis4.)