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A174063
Triangular array (read by rows) containing the least n integers < 2n such that no integer divides another.
2
1, 2, 3, 2, 3, 5, 2, 3, 5, 7, 4, 5, 6, 7, 9, 4, 5, 6, 7, 9, 11, 4, 5, 6, 7, 9, 11, 13, 4, 6, 7, 9, 10, 11, 13, 15, 4, 6, 7, 9, 10, 11, 13, 15, 17, 4, 6, 7, 9, 10, 11, 13, 15, 17, 19, 4, 6, 9, 10, 11, 13, 14, 15, 17, 19, 21, 4, 6, 9, 10, 11, 13, 14, 15, 17, 19, 21, 23, 4, 6, 9, 10, 11, 13, 14
OFFSET
1,2
COMMENTS
The first number on each row is 2^k, where k is the greatest integer such that (3^k)/2 < n.
EXAMPLE
1;
2, 3;
2, 3, 5;
2, 3, 5, 7;
4, 5, 6, 7, 9;
4, 5, 6, 7, 9, 11;
4, 5, 6, 7, 9, 11, 13;
4, 6, 7, 9, 10, 11, 13, 15;
MATHEMATICA
noneDivQ[L_] := NoneTrue[Subsets[L, {2}], Divisible[#[[2]], #[[1]]]&];
k1[n_] := For[k = Log[3, 2n]//Ceiling, True, k--, If[(3^k)/2<n, Return[k]]];
row[n_] := SelectFirst[Subsets[Range[2^k1[n], 2n-1], {n}], noneDivQ];
Array[row, 13] // Flatten (* Jean-François Alcover, Sep 25 2020 *)
CROSSREFS
Sequence in context: A138239 A361330 A112484 * A327277 A124459 A283360
KEYWORD
nonn,tabl
AUTHOR
David Brown, Mar 07 2010
EXTENSIONS
Definition corrected by David Brown, Mar 20 2010
STATUS
approved