A339922 Numbers k such that 20^k - 3 is prime.

1, 2, 5, 7, 9, 11, 15, 37, 59, 119, 154, 439, 745, 799, 1260, 1444, 3306, 8890, 14604, 15869, 20195, 99055, 186554, 396120

Offset: 1

Author

Paul Bourdelais, Dec 23 2020

Keywords

• nonn
• more

Examples

			1 is a term since 20^1 - 3 = 17 is a prime.
		

Crossrefs

Cf. A339921.

Programs

Mathematica

Do[ If[ PrimeQ[ 20^n - 3], Print[n]], {n, 0, 200000}]

PARI

is(n)=isprime(20^n - 3)

Extensions

a(24) from Paul Bourdelais, Jan 28 2021