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A355980 Indices of primes in A049685.

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%I A355980 #10 Dec 05 2023 16:43:23
%S A355980 2,3,6,9,15,21,44,50,114
%N A355980 Indices of primes in A049685.
%C A355980 Related to the search of solutions of the pair of congruences p^2 == -5 (mod q), q^2 == -5 (mod p).
%C A355980 Cosgrave and Dilcher list terms up to 25000, including probable primes.
%H A355980 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 A355980 A074281(n) = A049685(a(n)).
%F A355980 a(n) = (A074304(n)-1)/2.
%Y A355980 Cf. A049685, A074281, A074304.
%K A355980 nonn,more
%O A355980 1,1
%A A355980 _R. J. Mathar_, Jul 22 2022