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%I #18 Mar 22 2023 15:18:18
%S 2,5,41,21523361,926510094425921,1716841910146256242328924544641
%N Primes of the form (3^m + 1)/2.
%C Primes can only occur for m=2^k. The next term (if it exists) has k >= 21 (i.e., more than 10^6 decimal digits). - _Don Reble_, Apr 28 2004. [For the latest results about the search, see A171381. - _N. J. A. Sloane_, Jun 14 2010]
%C a(7) >= (3^(2^24) + 1)/2, if it exists. - _Tyler Busby_, Mar 22 2023
%e a(3)=41 because it can be written as (3^4 + 1)/2 = 82/2.
%Y A171381 is the main entry for this sequence. Cf. also A059917, A138083.
%K nonn,hard
%O 1,1
%A _Hugo Pfoertner_, Apr 19 2004
%E Erroneous terms deleted by _N. J. A. Sloane_, Jun 14 2010
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