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%I #21 Apr 03 2023 10:36:13
%S 2,5,14,124,399,4552,15898,203095,37029521,105973558438,
%T 19140185454656173
%N Indices of Wagstaff primes.
%H Andrew R. Booker, <a href="https://t5k.org/nthprime/">The Nth Prime Page</a>
%H C. Caldwell's The Top Twenty, <a href="https://t5k.org/top20/page.php?id=67">Wagstaff</a>.
%H Xavier Gourdon and Pascal Sebah, <a href="http://numbers.computation.free.fr/Constants/Primes/countingPrimes.html">Counting primes</a>
%H Tomás Oliveira e Silva, <a href="http://www.ieeta.pt/%7Etos/primes.html">Tables of values of pi(x) and of pi2(x)</a>
%H S. S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>.
%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Wagstaff_prime">Wagstaff prime</a>
%F a(n) = A000720(A000979(n)).
%F A000040(a(n)) = A000979(n).
%e For n = 3 the third Wagstaff prime is A000979(3) = 43 and 43 is also the 14th prime number, so a(3) = 14.
%o (PARI) default(primelimit, 10^9); forprime(p=3, 31, q=(2^p+1)/3; if(isprime(q), print1(primepi(q)", "))) \\ _Jens Kruse Andersen_, Jun 22 2014
%Y Cf. A000040, A000720, A000978, A000979, A059305, A123176, A126614, A194810.
%K nonn,hard,more
%O 1,1
%A _Omar E. Pol_, Jun 18 2014
%E a(11) from _Jens Kruse Andersen_, Jun 22 2014
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