OFFSET
1,1
LINKS
Mario Fernando Garcia Rivera, Table of n, a(n) for n = 1..47 (derived from A000043)
FORMULA
a(n) = (A000043(n+1) + 1)/2. - Charles R Greathouse IV, Aug 30 2010
a(n) = A146768(n) + 1. - César Aguilera, May 27 2020
EXAMPLE
2^(2*2 - 1) - 1 = 7;
2^(2*3 - 1) - 1 = 31;
2^(2*4 - 1) - 1 = 127.
MATHEMATICA
(MersennePrimeExponent[Range[2, 48]] + 1)/2 (* Amiram Eldar, Oct 22 2024 *)
PROG
(PARI) is(n)=isprime(2^(2*n-1)-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, May 13 2008
EXTENSIONS
More terms from Charles R Greathouse IV, Aug 30 2010
More terms from Mario Fernando Garcia Rivera, Jul 18 2022
STATUS
approved