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A171580
Least k such that k*(2^n)*((2^n-1)^2) - 1 is a prime number.
1
2, 2, 4, 3, 4, 5, 1, 6, 1, 5, 4, 3, 6, 5, 9, 7, 4, 5, 15, 19, 4, 27, 4, 12, 6, 38, 30, 5, 27, 13, 15, 2, 10, 7, 4, 7, 9, 32, 10, 2, 10, 33, 10, 2, 75, 17, 4, 5, 6, 12, 21, 6, 150, 14, 7, 11, 30, 27, 51, 29, 70, 58, 10, 10, 37, 45, 79, 212, 177, 17, 4, 33, 16, 54, 24, 20, 222, 105, 9, 83, 10
OFFSET
1,1
PROG
(PARI) a(n) = for(k=1, oo, if(ispseudoprime(k*(2^n)*((2^n-1)^2)-1), return(k))); \\ Jinyuan Wang, Feb 25 2020
CROSSREFS
Sequence in context: A140472 A109168 A015134 * A246796 A177235 A079707
KEYWORD
nonn
AUTHOR
Pierre CAMI, Dec 12 2009
EXTENSIONS
Extended by Ray Chandler, Dec 19 2009
STATUS
approved