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A137907
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.
3
1, 1, 9, 6, 9, 24, 4, 7, 28, 70, 73, 121, 511, 106, 343, 2169, 1423, 2146, 5736, 4444, 2484, 2310, 2679, 25623, 2481, 39213
OFFSET
1,3
EXAMPLE
1*(2^2-1)*(1*(2^2-1)-1)+1=7 prime, 2^2-1 first Mersenne prime, a(1)=1;
1*(2^3-1)*(1*(2^3-1)-1)+1=43 prime, 2^3-1 second Mersenne prime, a(2)=1.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Pierre CAMI, Feb 22 2008
EXTENSIONS
Corrected by Pierre CAMI, Jun 16 2012
STATUS
approved