login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A268692 Numbers n such that 2^(n-1)*(2^n - 1) + 1 is prime (see A134169). 0
1, 2, 3, 6, 9, 10, 13, 19, 45, 46, 58, 141, 271, 336, 562, 601, 1128, 1635, 2718, 2920, 3933, 4351, 4729, 6556, 8349, 10851, 32641, 34039, 41050 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The intersection of this sequence with A000043 gives 2, 3, 13, 19, ... which are the indices corresponding to primes just next to perfect numbers (A000396), see A061644.

There are prime members of this sequence (271, 601, 4729, ...) which are not in A000043.

a(30) > 50000. All the primes corresponding to terms up to a(29) have been certified by the PFGW software performing the Brillhart-Lehmer-Selfridge N-1 test. - Giovanni Resta, Apr 11 2016

LINKS

Table of n, a(n) for n=1..29.

PROG

(PARI) for(n=0, 10^5, ispseudoprime(2^(n-1)*(2^n-1)+1) && print1(n, ", "))

CROSSREFS

Cf. A134169, A061644, A000043, A000396, A006516.

Sequence in context: A190674 A188399 A047284 * A089160 A214974 A286434

Adjacent sequences:  A268689 A268690 A268691 * A268693 A268694 A268695

KEYWORD

nonn,more

AUTHOR

Jeppe Stig Nielsen, Feb 11 2016

EXTENSIONS

a(27)-a(29) from Giovanni Resta, Apr 11 2016

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 25 22:56 EDT 2022. Contains 356986 sequences. (Running on oeis4.)