|
%I #18 Feb 21 2022 02:16:21
%S 0,1,4,6,8,9,10,11,12,14,15,16,18,20,21,22,23,24,25,26,27,28,29,30,32,
%T 33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,
%U 56,57,58,59,60,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79
%N Numbers k such that 2^k - 1 is not prime.
%F Complement of A000043.
%e 8 belongs to the sequence because 2^8 - 1 = 255 is not a prime.
%t Select[Range[0,100],!PrimeQ[2^#-1]&] (* _Harvey P. Dale_, Mar 22 2011 *)
%o (Magma) [n: n in [0..100]| not IsPrime(2^n-1)] // _Vincenzo Librandi_, Jan 28 2011
%Y Cf. A000043 (Mersenne prime exponents), A054723 (primes of this sequence).
%K nonn,easy,nice
%O 1,3
%A _Felice Russo_
%E More terms from Jennifer D. Secor (s1175994(AT)cedarville.edu)
|
