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Primes in Sylvester's sequence A000058.
3

%I #24 Mar 11 2015 23:52:42

%S 2,3,7,43,3263443

%N Primes in Sylvester's sequence A000058.

%C No more primes up to 21st recurrence step. - _Artur Jasinski_, Sep 20 2008

%C Andersen's page shows that A000058(30) is the first number whose primality is unknown. Thus if a(6) exists it has over 218 million decimal digits.

%H Jens Kruse Andersen, <a href="http://primerecords.dk/sylvester-factors.htm">Factorization of Sylvester's sequence</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SylvestersSequence.html">Sylvester's Sequence</a>

%t a = {}; k = 2; Do[k = k^2 - k + 1; If[PrimeQ[k], AppendTo[a, k]], {n, 1, 15}]; a (* _Artur Jasinski_, Sep 20 2008 *)

%Y Cf. A000058.

%K nonn

%O 1,1

%A _Eric W. Weisstein_