%I #10 Dec 05 2023 16:43:23
%S 2,3,6,9,15,21,44,50,114
%N Indices of primes in A049685.
%C Related to the search of solutions of the pair of congruences p^2 == -5 (mod q), q^2 == -5 (mod p).
%C Cosgrave and Dilcher list terms up to 25000, including probable primes.
%H J. B. Cosgrave and K. Dilcher, <a href="https://fq.math.ca/Papers1/51-2/CosgraveDilcher-1.pdf">Pairs of reciprocal quadratic congruences involving primes</a>, Fib. Quart. 51 (2) (2013) 98, after Theorem 4.
%F A074281(n) = A049685(a(n)).
%F a(n) = (A074304(n)-1)/2.
%Y Cf. A049685, A074281, A074304.
%K nonn,more
%O 1,1
%A _R. J. Mathar_, Jul 22 2022