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
KEYWORD
nonn,more
AUTHOR
Paul Bourdelais, Dec 23 2020
EXTENSIONS
a(24) from Paul Bourdelais, Jan 28 2021
STATUS
approved