OFFSET

1,1

COMMENTS

Except the first term 4, all terms are odd since 2^(2*m) - 9 = (2^m - 3)*(2^m + 3) is not prime for m > 2.

LINKS

Keith Conrad, Square patterns and infinitude of primes, University of Connecticut, 2019.

Henri Lifchitz and Renaud Lifchitz (Editors), Search for 2^n-9, PRP Top Records.

EXAMPLE

243 is in the sequence because 2^243 - 9 is prime.

MATHEMATICA

Select[Range[3, 20000], PrimeQ[2^#-9]&] (* Vladimir Joseph Stephan Orlovsky, Feb 26 2011 *)

PROG

(PARI) is(n)=isprime(2^n-9) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

KEYWORD

nonn,more

AUTHOR

Andrey V. Kulsha, Feb 02 2001

EXTENSIONS

a(24)-a(25) from Max Alekseyev, a(26)-a(27) from Paul Underwood, added by Max Alekseyev, Feb 09 2012

a(28)-a(29) from Robert Price, Jan 25 2017

a(30) found by Stefano Morozzi, added by Elmo R. Oliveira, Nov 17 2023

STATUS

approved