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%I #13 Jan 29 2015 12:12:58
%S 4,2,26,10,466,506,128,13342,5974,8410
%N Smallest k such that 3^(3^n) - k is prime.
%C This is to 3 as A058220 is to 2.
%F a(n) = A064722(A055777(n)). - _Michel Marcus_, Jan 28 2015
%e a(4) = 10 because 3^(3^4) - 10 = 443426488243037769948249630619149892793 is prime.
%t lst={};Do[Do[p=3^(3^n)-k;If[PrimeQ[p],AppendTo[lst,k];Break[]],{k,2,11!}],{n,7}];lst (* _Vladimir Joseph Stephan Orlovsky_, Apr 27 2010 *)
%o (PARI) a(n) = x = 3^(3^n); x - precprime(x); \\ _Michel Marcus_, Jan 28 2015
%Y Cf. A055777 (3^(3^n)), A058220.
%K more,nonn
%O 1,1
%A _Jonathan Vos Post_, May 26 2008
%E a(5)-a(8) from _Cino Hilliard_, Jun 02 2008
%E a(9)-a(10) from _Donovan Johnson_, Sep 13 2008
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