A137909 Least k such that k*(2^p-1)*(k*(2^p-1)+1)+1 is prime, where 2^p-1 runs through the Mersenne primes.

1, 2, 2, 3, 17, 8, 3, 6, 96, 9, 224, 33, 260, 1044, 2397, 3, 1487, 657, 9602, 2133, 18438, 93, 17273, 32583, 66539, 9632, 1431, 100440, 150857

Offset: 1

Author

Pierre CAMI, Feb 22 2008

Keywords

• hard
• more
• nonn

Examples

			1*(2^2-1)*(1*(2^2-1)+1)+1=13 prime, 2^2-1 first Mersenne prime, a(1)=1
2*(2^3-1)*(2*(2^3-1)+1)+1=211 prime, 2^3-1 second Mersenne prime, a(2)=2
		

Crossrefs

Cf. A000043 (Mersenne exponents), A000668 (Mersenne primes).

Cf. A137906, A137907, A137908.

Extensions

a(27)-a(29) by Pierre CAMI, Oct 11 2014