A139286 -id:A139286 - cp's OEIS frontend

A139291 a(n) = 2^(2*prime(n) - 3) - 1.

1, 7, 127, 2047, 524287, 8388607, 2147483647, 34359738367, 8796093022207, 36028797018963967, 576460752303423487, 2361183241434822606847, 604462909807314587353087, 9671406556917033397649407, 2475880078570760549798248447, 10141204801825835211973625643007

Offset: 1

Omar E. Pol, Apr 13 2008

nonn

Cf. A139286, A139287, A139288, A139289, A139290, A139293, A139294, A139306.

(2^(2#-1))/4-1&/@Prime[Range[20]] (* Harvey P. Dale, May 08 2011 *)

a(n) = A139286(n)/4 - 1.
a(n) = A000225(A131426(n)). - Max Alekseyev, Mar 07 2020
a(n) = A139290(n) - 1. - Omar E. Pol, Mar 10 2020

Edited by Max Alekseyev, May 03 2009, Mar 07 2020

A139314 Primes of the form 2^(2p - 1) - 1, where p is prime.

Original entry on oeis.org

7, 31, 8191, 2305843009213693951

Offset: 1

Omar E. Pol, Apr 13 2008

nonn

Primes in A139287.
This sequence is a subsequence of A000668. From A000043, a(5) = 2^3217 - 1.
The next term a(6) is an unknown Mersenne prime. [Washington Bomfim, Nov 18 2009]
a(5) has 969 digits. - Vincenzo Librandi, Dec 14 2010
The first three terms can be written as (n^3 - 1)/(n - 1) for some n. [Arkadiusz Wesolowski, May 09 2012]

Michel Marcus, Table of n, a(n) for n = 1..5
Wikipedia, Mersenne prime

Cf. A139286, A139287.

Cf. A000668, A000043. [Washington Bomfim, Nov 18 2009]

[a: p in PrimesUpTo(4200) | IsPrime(a) where a is 2^(2*p-1)-1]; // Vincenzo Librandi, Dec 14 2010

cp's OEIS Frontend

A139291 a(n) = 2^(2*prime(n) - 3) - 1.

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A139314 Primes of the form 2^(2p - 1) - 1, where p is prime.

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