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%I #29 Jul 14 2023 15:15:44
%S 1,2,3,11,30,62,534,620,803,2436,2669,3975,4530,4827,5294,15987,17589,
%T 51960
%N Numbers k such that 2*(3^k-k)-1 is prime.
%C According to Maple version 14, the next entries are 534, 620 and 803, but these involve primes of 256 and more digits and may not be certified primes. - _R. J. Mathar_, Sep 23 2011
%e 1 is in the sequence because 2*3^1-2*1-1 = 3 is a prime, 2 is in the sequence because 2*3^2-2*2-1 = 13 is a prime, 3 is in the sequence because 2*3^3-2*3-1=47 ts a prime, 4 is not in the sequence because 2*3^4-2*4-1 = 153 = 3^2*17 is not prime.
%o (PARI) is(n)=ispseudoprime(2*(3^n-n)-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A048473.
%K nonn,more
%O 1,2
%A _Juri-Stepan Gerasimov_, Sep 23 2011
%E a(10)-a(18) from _Michael S. Branicky_, Jul 14 2023
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