Definition of Merssene number

Does the definition of Merssene number( 2^n-1) requires
that n must be prime ?

[CRGreathouse]

Both definitions, unfortunately, are in use. The more common one requires that the exponent is prime.
http://oeis.org/classic/A001348
http://oeis.org/classic/A000225

[ATH]

Mathworld uses 2ⁿ-1 where n is integer:

http://mathworld.wolfram.com/MersenneNumber.html


Maybe OP wonders why GIMPS searches only prime exponents, its because 2ⁿ-1 can only be prime when n is prime: http://primes.utm.edu/notes/proofs/Theorem2.html

[science_man_88]

No definitions were found for merssene number. Google lol.

[CRGreathouse]

Originally Posted by science_man_88

No definitions were found for merssene number. Google lol.

Really? I get
http://www.google.com/search?q=define:Mersenne+number

In mathematics, a Mersenne number, named after Marin Mersenne, is a positive integer that is one less than a power of two: Some definitions of Mersenne numbers require that the exponent p be prime.
en.wikipedia.org/wiki/Mersenne_Number

[TimSorbet]

Originally Posted by CRGreathouse

Really? I get
http://www.google.com/search?q=define:Mersenne+number

Perhaps he tried to get the definition of "merssene number" instead of "mersenne number". "No definitions were found for merssene number." is very true.