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

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

Offset: 1

Author

Jeppe Stig Nielsen, Jul 03 2023

Keywords

• nonn
• hard
• more

Comments

Such primes are sometimes called Carol primes of base 20.

Links

• Prime-Wiki, Carol-Kynea prime.
• Eric Weisstein's World of Mathematics, Near-Square Prime.

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.

Programs

PARI

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