login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A325860 Number of subsets of {1..n} such that every pair of distinct elements has a different quotient. 20
1, 2, 4, 8, 14, 28, 52, 104, 188, 308, 548, 1096, 1784, 3568, 6168, 10404, 16200, 32400, 49968, 99936, 155584, 256944, 433736, 867472, 1297504, 2026288 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Also subsets of {1..n} such that every orderless pair of (not necessarily distinct) elements has a different product.

LINKS

Table of n, a(n) for n=0..25.

EXAMPLE

The a(0) = 1 through a(4) = 14 subsets:

  {}  {}   {}    {}     {}

      {1}  {1}   {1}    {1}

           {2}   {2}    {2}

           {12}  {3}    {3}

                 {12}   {4}

                 {13}   {12}

                 {23}   {13}

                 {123}  {14}

                        {23}

                        {24}

                        {34}

                        {123}

                        {134}

                        {234}

MATHEMATICA

Table[Length[Select[Subsets[Range[n]], UnsameQ@@Divide@@@Subsets[#, {2}]&]], {n, 0, 20}]

CROSSREFS

The subset case is A325860.

The maximal case is A325861.

The integer partition case is A325853.

The strict integer partition case is A325854.

Heinz numbers of the counterexamples are given by A325994.

Cf. A002033, A108917, A143823, A196723, A196723, A196724, A325855, A325858, A325859, A325868, A325869.

Sequence in context: A096590 A068912 A164176 * A217932 A215978 A018086

Adjacent sequences:  A325857 A325858 A325859 * A325861 A325862 A325863

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, May 31 2019

EXTENSIONS

a(21)-a(25) from Alois P. Heinz, Jun 07 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 27 03:03 EDT 2020. Contains 334647 sequences. (Running on oeis4.)