A364080 Numbers k such that (20^k - 1)^2 - 2 is prime.

1, 2, 53, 183, 1281, 1300, 8041, 29936, 72820

Offset

1,2

Comments

Such primes are sometimes called Carol primes of base 20.

Links

Table of n, a(n) for n=1..9.

Prime-Wiki, Carol-Kynea prime.

Eric Weisstein's World of Mathematics, Near-Square Prime.

Prog

(PARI) for(k=1, 1200, ispseudoprime((20^k-1)^2-2)&&print1(k, ", "))

Crossrefs

Cf. A091515 (b=2), A100901 (b=6), A100903 (b=10), A364076 (b=12), A100905 (b=14), A364078 (b=18), A100907 (b=22).

Cf. A364081.

Sequence in context: A249662 A249663 A130698 * A248988 A248989 A248990

Adjacent sequences: A364077 A364078 A364079 * A364081 A364082 A364083

Keyword

nonn,hard,more

Author

Jeppe Stig Nielsen, Jul 03 2023

Status

approved