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A159585
Nearest k to j such that k*(2^j-1)+1 is prime where j=A000043(n) and 2^j-1 = Mersenne-prime(n) = A000668(n). If there are two k values equidistant from j, each of which produces a prime, the larger of the two gets added to the sequence.
1
2, 4, 10, 4, 46, 22, 16, 46, 66, 136, 166, 124, 636, 550, 1474, 3066, 1656, 1816, 3708, 9436, 1746, 3696, 11262, 40138, 25900, 20808, 60340, 58818
OFFSET
1,1
EXAMPLE
n=6, j=A000043(6)=17, A000668(6)=131071, then k=12 or k=22 are the nearest values to j which produce primes so we take the larger of the two k values for a(6)=22.
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Ray Chandler, Apr 16 2009
STATUS
approved