login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A045762 Numbers n such that 2^n-1 is not prime. 1
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; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..71.

FORMULA

Complement of A000043.

EXAMPLE

8 belongs to the sequence because 2^8-1=255 is not a prime.

MATHEMATICA

Select[Range[0, 100], !PrimeQ[2^#-1]&]  (* Harvey P. Dale, Mar 22 2011 *)

PROG

(MAGMA) [n: n in [0..100]| not IsPrime(2^n-1)] // Vincenzo Librandi, Jan 28 2011

CROSSREFS

Cf. A000043 (Mersenne prime exponents), A054723 (primes of this sequence).

Sequence in context: A091985 A091984 A228651 * A320985 A047748 A299540

Adjacent sequences:  A045759 A045760 A045761 * A045763 A045764 A045765

KEYWORD

nonn,easy,nice

AUTHOR

Felice Russo

EXTENSIONS

More terms from Jennifer D. Secor (s1175994(AT)cedarville.edu)

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 14 10:04 EST 2019. Contains 329111 sequences. (Running on oeis4.)