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A024843
a(n) = least m such that if r and s in {1/1, 1/2, 1/3, ..., 1/n} satisfy r < s, then r < k/m < (k+3)/m < s for some integer k.
3
9, 23, 43, 69, 101, 139, 183, 233, 289, 361, 431, 518, 601, 703, 799, 916, 1025, 1157, 1279, 1426, 1561, 1723, 1871, 2048, 2209, 2401, 2601, 2783, 2998, 3221, 3423, 3661, 3907, 4129, 4390, 4659, 4901, 5185, 5477, 5739, 6046, 6361, 6643, 6973, 7311, 7613, 7966, 8327, 8649
OFFSET
2,1
COMMENTS
For a guide to related sequences, see A001000. - Clark Kimberling, Aug 08 2012
LINKS
EXAMPLE
Using the terminology introduced at A001000, the 4th separator of the set {1/3, 1/2, 1} is a(3) = 23, since 1/3 < 8/23 < 11/23 < 1/2 < 12/23 < 15/23 < 1 and 23 is the least m for which 1/3, 1/2, 1 are thus separated using numbers k/m. - Clark Kimberling, Aug 08 2012
MATHEMATICA
leastSeparatorS[seq_, s_] := Module[{n = 1},
Table[While[Or @@ (Ceiling[n #1[[1]]] <
s + 1 + Floor[n #1[[2]]] &) /@ (Sort[#1, Greater] &) /@
Partition[Take[seq, k], 2, 1], n++]; n, {k, 2, Length[seq]}]];
t = Map[leastSeparatorS[1/Range[50], #] &, Range[5]];
TableForm[t]
t[[4]] (* Peter J. C. Moses, Aug 08 2012 *)
CROSSREFS
Cf. A001000.
Sequence in context: A147395 A302906 A144390 * A363161 A183453 A296311
KEYWORD
nonn
STATUS
approved