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A339922
Numbers k such that 20^k - 3 is prime.
1
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
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
KEYWORD
nonn,more
AUTHOR
Paul Bourdelais, Dec 23 2020
EXTENSIONS
a(24) from Paul Bourdelais, Jan 28 2021
STATUS
approved