

A050920


Cullen primes: primes of the form n*2^n+1.


5




OFFSET

1,1


COMMENTS

The next term is too large to display here, having 1423 digits. See A005849.


LINKS

Table of n, a(n) for n=1..2.
Ray Ballinger, Cullen Primes: Definition and Status
Chris K. Caldwell, Cullen Primes
Eric Weisstein's World of Mathematics, Cullen Number


FORMULA

a(n) = A002064(A005849(n)).


EXAMPLE

1 * 2^1 + 1 = 3, which is prime.
141 * 2^141 + 1 = 393050634124102232869567034555427371542904833, which is also prime.
The third Cullen prime is approximately 2.677114856136697933736444 * 10^1422.


MATHEMATICA

Select[Table[n * 2^n + 1, {n, 5000}], PrimeQ] (* Harvey P. Dale, Dec 14 2014 *)


CROSSREFS

See A005849 for the corresponding n.
Sequence in context: A068740 A058473 A115527 * A001231 A089418 A274981
Adjacent sequences: A050917 A050918 A050919 * A050921 A050922 A050923


KEYWORD

nonn,nice,bref


AUTHOR

N. J. A. Sloane, Dec 30 1999


STATUS

approved



