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A045762
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Numbers n such that 2^n-1 is not prime.
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0
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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, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| Complement of A000043.
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EXAMPLE
| 8 belongs to the sequence because 2^8-1=255 is not a prime.
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MATHEMATICA
| Select[Range[0, 100], !PrimeQ[2^#-1]&] (* From Harvey P. Dale, Mar 22 2011 *)
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PROG
| (MAGMA) [n: n in [0..100]| not IsPrime(2^n-1)] [From Vincenzo Librandi, Jan 28 2011]
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CROSSREFS
| Cf. Mersenne prime exponents A000043.
Sequence in context: A031977 A091985 A091984 * A047748 A085558 A084984
Adjacent sequences: A045759 A045760 A045761 * A045763 A045764 A045765
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KEYWORD
| nonn,easy,nice
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AUTHOR
| Felice Russo (frusso(AT)micron.com)
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EXTENSIONS
| More terms from Jennifer D. Secor (s1175994(AT)cedarville.edu)
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