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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 (list; graph; refs; listen; history; text; internal format)
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 * A196255 A024666 A184397

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

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Last modified August 1 22:36 EDT 2021. Contains 346408 sequences. (Running on oeis4.)