OFFSET
1,1
COMMENTS
A135979 is a subsequence of this sequence.
FORMULA
prime(a(n)) = A054723(n).
MATHEMATICA
k = {}; Do[If[ ! PrimeQ[2^Prime[n] - 1], AppendTo[k, n]], {n, 1, 40}]; k
m = PrimePi @ MersennePrimeExponent @ Range[13]; Complement[Range[m[[-1]]], m] (* Amiram Eldar, Mar 12 2020 *)
PROG
(PARI) isok(k) = !isprime(2^prime(k)-1); \\ Michel Marcus, Mar 12 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Artur Jasinski, Dec 09 2007
EXTENSIONS
More terms from Amiram Eldar, Mar 12 2020
STATUS
approved