login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A339922 Numbers k such that 20^k - 3 is prime. 1

%I

%S 1,2,5,7,9,11,15,37,59,119,154,439,745,799,1260,1444,3306,8890,14604,

%T 15869,20195,99055,186554,396120

%N Numbers k such that 20^k - 3 is prime.

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

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

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

%Y Cf. A339921.

%K nonn,more

%O 1,2

%A _Paul Bourdelais_, Dec 23 2020

%E a(24) from _Paul Bourdelais_, Jan 28 2021

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 16 21:28 EDT 2021. Contains 347473 sequences. (Running on oeis4.)