A107709 Least odd prime a(n) such that (a(n)*M(n))^2 + a(n)*M(n) - 1 is prime with M(n) = Mersenne-primes (A000043).

3, 3, 3, 7, 43, 19, 13, 5, 571, 3, 137, 59, 3823, 2707, 6277, 1063, 4523, 631, 8209, 34537, 102329, 46399, 30323, 18803, 1063, 21019

Offset

1,1

Links

Table of n, a(n) for n=1..26.

Example

M(1)=2^2-1=3, (3*3)^2 + 3*3 -1 = 89 prime so a(1)=3.
M(2)=2^3-1=7, (3*7)^2 + 3*7 -1 = 461 prime so a(2)=3.
M(3)=2^5-1=31, (3*31)^2 + 3*31 -1 = 8741 prime so a(3)=3.
M(4)=2^7-1=127, (7*127)^2 + 7*127 -1 = 791209 prime so a(4)=7.

Crossrefs

Cf. A000043.

Sequence in context: A098524 A143015 A295671 * A111521 A177937 A029628

Adjacent sequences: A107706 A107707 A107708 * A107710 A107711 A107712

Keyword

hard,more,nonn

Author

Pierre CAMI, Jun 10 2005

Extensions

a(23)-a(26) from Pierre CAMI, Nov 21 2011

Status

approved