A174063 Triangular array (read by rows) containing the least n integers < 2n such that no integer divides another.

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.

Links

Table of n, a(n) for n=1..85.

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

Cf. A174062, A174094.

Sequence in context: A138239 A361330 A112484 * A327277 A124459 A283360

Adjacent sequences: A174060 A174061 A174062 * A174064 A174065 A174066

Keyword

nonn,tabl

Author

David Brown, Mar 07 2010

Extensions

Definition corrected by David Brown, Mar 20 2010

Status

approved