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

Author

Pierre CAMI, Jun 10 2005

Keywords

• hard
• more
• nonn

Examples

			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.

Extensions

More terms from Pierre CAMI, Nov 21 2011