A364081 Numbers k such that (20^k + 1)^2 - 2 is prime.

1, 15, 44, 77, 141, 208, 304, 1169, 3359, 5050, 22431, 34935, 92990

Offset

1,2

Comments

Such primes are sometimes called Kynea primes of base 20.

Links

Table of n, a(n) for n=1..13.

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. A091513 (b=2), A100902 (b=6), A100904 (b=10), A364077 (b=12), A100906 (b=14), A364079 (b=18), A100908 (b=22).

Cf. A364080.

Sequence in context: A133343 A027845 A201810 * A292018 A289669 A295980

Adjacent sequences: A364078 A364079 A364080 * A364082 A364083 A364084

Keyword

nonn,hard,more

Author

Jeppe Stig Nielsen, Jul 03 2023

Status

approved