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A125684
Numbers k such that A125683(k) is prime.
2
3, 4, 5, 6, 7, 8, 10, 13, 14, 18, 21, 22, 26, 27, 28, 32, 33, 35, 51, 54, 58, 67, 76, 89, 100, 140, 170, 189, 269, 307, 365, 408, 470, 475, 546, 558, 604, 751, 771, 857, 892, 896, 992, 1031, 1080, 1181, 1228, 1289, 1342, 1465, 1483, 1491, 1520, 1525, 1571, 1620
OFFSET
1,1
COMMENTS
Corresponding primes are listed in A125685(n) = A125683(a(n)).
EXAMPLE
A125683(n) begins {1,1,5,11,2,79,331,479,493,5297,2701,69071,70061,...}.
Thus a(1) = 3 because A125683(3) = 5 is the first prime.
a(2)-a(6) = {4,5,6,7,8} because A125683(k) is prime for 3<k<9.
MATHEMATICA
g=0; Do[g=g+(-1)^(n+1)*1/(n(n+1)); f=Numerator[g]; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1342}]
CROSSREFS
Sequence in context: A039078 A073632 A066378 * A207669 A001272 A273664
KEYWORD
hard,nonn
AUTHOR
Alexander Adamchuk, Nov 30 2006
EXTENSIONS
More terms from Amiram Eldar, Feb 18 2019
STATUS
approved