A137909 - OEIS

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

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OFFSET

1,2

LINKS

EXAMPLE

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).

KEYWORD

hard,more,nonn

AUTHOR

Pierre CAMI, Feb 22 2008

EXTENSIONS

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

STATUS

approved