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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A095991 Numbers n such that f(k) * 2^n - 1 is prime, where f(j) = A070826(j) and k is the number of decimal digits of 2^n. 0
2, 3, 4, 6, 14, 17, 18, 23, 33, 43, 45, 53, 60, 70, 114, 141, 162, 178, 387, 657, 787, 951, 1517, 1882, 1999, 2423, 2722, 3635, 3636, 3893, 5021, 5631 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(1) through a(32) have been proved to be prime with WinPFGW. a(32) has 7901 digits. No more terms up to 7300.

LINKS

Table of n, a(n) for n=1..32.

PFGW, Discussion group for the PrimeForm program.

EXAMPLE

a(5)=14 because 1155 * 2^14 - 1 = 18923519, a prime.

MATHEMATICA

Do[ If[ PrimeQ[ Product[ Prime[i], {i, Floor[ n / Log[2, 10] + 1]}] * 2^(n - 1) - 1], Print[n]], {n, 7300}] (* Robert G. Wilson v, Jul 23 2004 *)

CROSSREFS

Sequence in context: A038767 A188715 A174046 * A293714 A049911 A056712

Adjacent sequences:  A095988 A095989 A095990 * A095992 A095993 A095994

KEYWORD

more,nonn,base

AUTHOR

Jason Earls, Jul 18 2004

EXTENSIONS

Edited by Robert G. Wilson v, Jul 23 2004

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 August 20 01:14 EDT 2019. Contains 326136 sequences. (Running on oeis4.)