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A049095 Numbers k such that 2^k + 1 is squarefree. 4

%I #14 Jun 30 2017 03:02:58

%S 1,2,4,5,6,7,8,11,12,13,14,16,17,18,19,20,22,23,24,25,26,28,29,31,32,

%T 34,35,36,37,38,40,41,42,43,44,46,47,48,49,52,53,54,56,58,59,60,61,62,

%U 64,65,66,67,71,72,73,74,76,77,79,80,82,83,84,85,86,88,89,91,92,94,95

%N Numbers k such that 2^k + 1 is squarefree.

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

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

%t Select[Range@ 95, SquareFreeQ[2^# + 1] &] (* _Michael De Vlieger_, Jun 29 2017 *)

%o (PARI) isok(n) = issquarefree(2^n + 1); \\ _Michel Marcus_, Dec 18 2013

%Y Complement of A049096.

%K nonn

%O 1,2

%A _Labos Elemer_

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)