A355980 Indices of primes in A049685.

2, 3, 6, 9, 15, 21, 44, 50, 114

Offset: 1

Author

R. J. Mathar, Jul 22 2022

Keywords

• nonn
• more

Comments

Related to the search of solutions of the pair of congruences p^2 == -5 (mod q), q^2 == -5 (mod p).

Cosgrave and Dilcher list terms up to 25000, including probable primes.

Links

• J. B. Cosgrave and K. Dilcher, Pairs of reciprocal quadratic congruences involving primes, Fib. Quart. 51 (2) (2013) 98, after Theorem 4.

Crossrefs

Cf. A049685, A074281, A074304.

Formula

A074281(n) = A049685(a(n)).

a(n) = (A074304(n)-1)/2.