A098818 Smallest k such that k*Mersenne_prime(n)^2 -1 (or k*A000668(n)^2 -1) is prime.

2, 2, 8, 2, 12, 2, 2, 98, 38, 122, 126, 678, 440, 1040, 776, 1398, 2714, 3362, 650, 8910, 22010, 11172, 1422, 5274, 33944, 4508, 12614, 202298, 275466

Offset

1,1

Links

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

Example

2*((2^2-1)^2)-1=17 prime so a(1)=2.

Crossrefs

Cf. A000668

Sequence in context: A174354 A011147 A273168 * A092694 A098984 A088560

Adjacent sequences: A098815 A098816 A098817 * A098819 A098820 A098821

Keyword

more,nonn

Author

Pierre CAMI, Oct 08 2004

Extensions

a(19)-a(22) from Donovan Johnson, Mar 23 2008

a(23)-a(29) from Pierre CAMI, Feb 15 2014

Status

approved