1,2

Table of n, a(n) for n=1..71.

8 is in the sequence because 2^8 + 1 = 257 is prime, hence it is squarefree.

9 is not in the sequence because 2^9 + 1 = 513 is divisible by a square, 9.

Select[Range@ 95, SquareFreeQ[2^# + 1] &] (* Michael De Vlieger, Jun 29 2017 *)

(PARI) isok(n) = issquarefree(2^n + 1); \\ Michel Marcus, Dec 18 2013

Complement of A049096.

Sequence in context: A276706 A271396 A070110 * A324583 A101742 A194831

Adjacent sequences: A049092 A049093 A049094 * A049096 A049097 A049098

nonn

Labos Elemer

approved