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

1,2

Links

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A339921.

Sequence in context: A286991 A029905 A057437 * A359071 A196255 A024666

Adjacent sequences: A339919 A339920 A339921 * A339923 A339924 A339925

Keyword

nonn,more

Author

Paul Bourdelais, Dec 23 2020

Extensions

a(24) from Paul Bourdelais, Jan 28 2021

Status

approved