A156560 Primes of the form 2^n-5.

3, 11, 59, 251, 1019, 4091, 262139, 1048571, 67108859, 4294967291, 68719476731, 72057594037927931, 73786976294838206459, 332306998946228968225951765070086139, 1361129467683753853853498429727072845819, 1427247692705959881058285969449495136382746619

Offset

1,1

Comments

If p = 2^n-5 is prime, then p*2^(n-1) is abundant with abundance 4 (see A088832). - Davide Rotondo, Oct 25 2020

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..28

Formula

a(n) = 2^A059608(n) - 5.

Mathematica

Select[Table[2^n-5, {n, 2, 400}], PrimeQ] (* Vincenzo Librandi, Jul 26 2012 *)

Prog

(Magma) [ a: n in [2..500] | IsPrime(a) where a is 2^n-5 ]
(PARI) for(n=1, 300, q=2^n-5; if(isprime(q), print(q))) /* gives more terms in <10secs */ \\ Joerg Arndt, Dec 03 2010

Crossrefs

Corresponding n's are in A059608.

Cf. A088832.

Sequence in context: A319248 A340865 A290484 * A028342 A137982 A193364

Adjacent sequences: A156557 A156558 A156559 * A156561 A156562 A156563

Keyword

nonn

Author

Vincenzo Librandi, Feb 10 2009

Extensions

Edited by Zak Seidov

Status

approved