A355980 Indices of primes in A049685.

2, 3, 6, 9, 15, 21, 44, 50, 114, 146, 228, 270, 326, 329, 776, 1001, 1353, 1374, 3579, 5144, 13133, 29790, 31710, 40455

Offset

1,1

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

Table of n, a(n) for n=1..24.

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

Formula

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

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

Crossrefs

Cf. A049685, A074281, A074304.

Sequence in context: A168497 A256975 A364841 * A239882 A086642 A308930

Adjacent sequences: A355977 A355978 A355979 * A355981 A355982 A355983

Keyword

nonn,more

Author

R. J. Mathar, Jul 22 2022

Extensions

a(10)-a(24) from Michael S. Branicky, Dec 18 2025 using A074304

Status

approved