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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A121371 Least number k such that (k*M(n))^2 + k*M(n) - 1 and (k*M(n))^2 + k*M(n) + 1 are twin primes with M(i)=i-th Mersenne prime. 1
1, 3, 5, 8, 99, 275, 278, 409, 96, 1538, 1253, 15858, 189168, 119552, 221444, 1047122, 3571449 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..17.

EXAMPLE

M(2)=2^3-1=7

7^2+7-1=55 composite

(2*7)^2+2*7-1=209 composite

(3*7)^2+3*7-1=461 prime, 461 and 463 are twin primes so k(2)=3

CROSSREFS

Cf. A121370.

Sequence in context: A174529 A174442 A109342 * A067094 A058642 A141251

Adjacent sequences:  A121368 A121369 A121370 * A121372 A121373 A121374

KEYWORD

hard,more,nonn

AUTHOR

Pierre CAMI, Jul 24 2006

STATUS

approved

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

Content is available under The OEIS End-User License Agreement .

Last modified October 25 20:39 EDT 2014. Contains 248557 sequences.