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A325868 Number of subsets of {1..n} containing n such that every ordered pair of distinct elements has a different quotient. 9
1, 2, 4, 6, 14, 24, 52, 84, 120, 240, 548, 688, 1784, 2600, 4236, 5796, 16200, 17568, 49968, 55648 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

The a(1) = 1 through a(5) = 14 subsets:

  {1}  {2}    {3}      {4}      {5}

       {1,2}  {1,3}    {1,4}    {1,5}

              {2,3}    {2,4}    {2,5}

              {1,2,3}  {3,4}    {3,5}

                       {1,3,4}  {4,5}

                       {2,3,4}  {1,2,5}

                                {1,3,5}

                                {1,4,5}

                                {2,3,5}

                                {2,4,5}

                                {3,4,5}

                                {1,2,3,5}

                                {1,3,4,5}

                                {2,3,4,5}

MATHEMATICA

Table[Length[Select[Subsets[Range[n]], MemberQ[#, n]&&UnsameQ@@Divide@@@Subsets[#, {2}]&]], {n, 10}]

CROSSREFS

Cf. A025582, A108917, A143823, A196723, A196724.

Cf. A325853, A325854, A325858, A325860, A325861, A325864, A325869.

Sequence in context: A307676 A084685 A219042 * A251581 A151794 A181528

Adjacent sequences:  A325865 A325866 A325867 * A325869 A325870 A325871

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Jun 02 2019

STATUS

approved

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Last modified August 26 02:19 EDT 2019. Contains 326324 sequences. (Running on oeis4.)