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%I #10 Apr 03 2023 10:36:11
%S 2,3,4,5,6,7,8,9,11,14,18,22,26,31,39,43,46,65,69,126,267,380,495,762,
%T 1285,1304,1364,1479,1697,4469,8135,9193,11065,11902,12923,13103,
%U 23396,23642,31850,77509,285228
%N Numbers n such that (2^p + 1)/3 is prime, where p is the n-th prime.
%C Also prime(a(n)) are the indices of prime Jacobsthal numbers (A001045) with prime indices. Primes in the Jacobsthal sequence are listed in A049883.
%H C. Caldwell's The Top Twenty, <a href="https://t5k.org/top20/page.php?id=67">Wagstaff</a>.
%F a(n) = A000720( A000978(n) ).
%t Select[Range[500],PrimeQ[(2^Prime[#]+1)/3]&] (* The program generates the first 23 terms of the sequence. To generate more, increase the Range constant. *) (* _Harvey P. Dale_, Mar 09 2022 *)
%Y Cf. A000978, A000979, A001045, A049883, A107036, A123214.
%K more,nonn
%O 1,1
%A _Alexander Adamchuk_, Oct 03 2006
%E Two more terms computed from A000978 by _Max Alekseyev_, Mar 03 2010
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