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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A131458 Residues of 3^(2^(p(n)-1)-1) for Mersenne numbers with prime indices. 6
0, 6, 30, 126, 1565, 8190, 131070, 524286, 7511964, 89777599, 2147483646, 20166585982, 840455563322, 4787976306682, 5519162753736, 2617809209727498, 334169564069012755, 2305843009213693950, 47306781863857413639 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Mp is prime iff 3^(2^(p(n)-1)-1) is congruent to (-1) Mod Mp. Thus M7 = 127 is prime because 3^63 Mod 127 = 126 (=127-1) while M11 = 2047 is composite because 3^1023 Mod 2047 <> 2046.

LINKS

Dennis Martin, Table of n, a(n) for n = 1..100

FORMULA

a(n) = 3^(2^(p(n)-1)-1) Mod 2^p(n)-1

EXAMPLE

a(5) = 3^(2^(11-1)-1) Mod 2^11-1 = 3^1023 Mod 2047 = 1565

CROSSREFS

Cf. A095847, A001348, A131459, A131460, A131461, A131462, A131463.

Sequence in context: A002446 A002934 A174319 * A032205 A007465 A261389

Adjacent sequences:  A131455 A131456 A131457 * A131459 A131460 A131461

KEYWORD

nonn

AUTHOR

Dennis Martin (dennis.martin(AT)dptechnology.com), Jul 13 2007, Jul 20 2007

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 February 20 22:51 EST 2019. Contains 320362 sequences. (Running on oeis4.)