A109342 Least k such that (k*M(n))^2+k*M(n)-1 is the first of a pair of twin primes, where M(n) = Mersenne primes.

1, 3, 5, 8, 89, 275, 278, 404, 96, 1538, 1253, 15858, 189168, 119552, 636315, 1047122, 3571449

Offset

1,2

Links

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

Example

(3*M(2))^2+3*M(2)-1 = (3*7)^2+3*7-1 = 461, 461 and 463 twin primes so for n=2 k=3

Crossrefs

Cf. A000043.

Sequence in context: A195548 A174529 A174442 * A121371 A067094 A272235

Adjacent sequences: A109339 A109340 A109341 * A109343 A109344 A109345

Keyword

hard,nonn

Author

Pierre CAMI, Aug 21 2005; corrected Apr 06 2006

Status

approved