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A054723 Prime exponents of nonprime Mersenne numbers. 11
11, 23, 29, 37, 41, 43, 47, 53, 59, 67, 71, 73, 79, 83, 97, 101, 103, 109, 113, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331 (list; graph; refs; listen; history; internal format)
OFFSET

0,1

EXAMPLE

p=29 is included because 29 is prime, but 2^29-1 is *not* prime.

MATHEMATICA

Select[Prime[Range[70]], ! PrimeQ[2^# - 1] &]  [From Harvey P. Dale, Feb. 3, 2011]

CROSSREFS

Complement of A000043 inside A000040. No proof is known that this sequence is infinite!

Cf. A000043, A016027.

Sequence in context: A058340 A138537 A136000 * A109981 A091367 A088136

Adjacent sequences:  A054720 A054721 A054722 * A054724 A054725 A054726

KEYWORD

easy,nonn

AUTHOR

Jeppe Stig Nielsen (sequence(AT)jeppesn.dk), Apr 20 2000

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Last modified February 15 23:32 EST 2012. Contains 205860 sequences.