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%I #22 Apr 01 2018 20:27:50
%S 2,3,2,3,444
%N Smallest integer x > 1 such that x^x + n is prime, or 0 if no such x exists.
%C The sequence with the unknown terms indicated by ?: 2, 3, 2, 3, 444, ?, 2, ?, 2, 3, ?, 5, 2, 3, 2, 3, ?, 19, 2, 3, 4, 19, 6, ?, 2, 3, 2, 15, 30, 7, 6, 3, 2, 3, 6, ?, 2, 5, 2, 3, ...
%C The unknown terms a(6), a(8), a(11), a(17), a(24), a(36) are > 6000.
%C It is conjectured that such x always exists. - _Dean Hickerson_
%C We can show that for all n=(6k-1)^3, k > 0, there is no such x, which disproves the conjecture. See the main entry A087037 for more details. - _Farideh Firoozbakht_ and _M. F. Hasler_, Nov 27 2009
%H OpenPFGW Project, <a href="http://www.primeform.net/openpfgw/">Primality Tester</a>
%e a(4)=3 because 3^3 + 4 = 27 + 4 = 31 is prime.
%Y Cf. A000312 (n^n), A087037 (x^x+n is prime, x>0).
%K nonn,more
%O 1,1
%A _Hugo Pfoertner_, Jul 31 2003
%E Name edited by _Altug Alkan_, Apr 01 2018
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