OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..18
FORMULA
MAPLE
a:= n-> prevprime(numtheory[mersenne]([n])):
seq(a(n), n=1..12); # Alois P. Heinz, Oct 30 2024
MATHEMATICA
NextPrime[Select[2^Prime[Range[50]] - 1, PrimeQ], -1] (* Jayanta Basu, Jul 08 2013 *)
Table[NextPrime[2^MersennePrimeExponent[n] - 1, -1], {n, 1, 12}] (* Amiram Eldar, Aug 10 2024 *)
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Labos Elemer, Aug 05 2002
STATUS
approved