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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A326495 Number of subsets of {1..n} containing no sums or products of pairs of elements. 8
 1, 1, 2, 4, 6, 11, 17, 30, 45, 71, 101, 171, 258, 427, 606, 988, 1328, 2141, 3116, 4952, 6955, 11031, 15320, 23978, 33379, 48698, 66848, 104852, 144711, 220757, 304132, 461579, 636555, 973842, 1316512, 1958827, 2585432, 3882842, 5237092, 7884276, 10555738, 15729292 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS The pairs are not required to be strict. LINKS FORMULA For n > 0, a(n) = A326490(n) - 1. EXAMPLE The a(1) = 1 through a(6) = 17 subsets:   {}  {}   {}     {}     {}       {}       {2}  {2}    {2}    {2}      {2}            {3}    {3}    {3}      {3}            {2,3}  {4}    {4}      {4}                   {2,3}  {5}      {5}                   {3,4}  {2,3}    {6}                          {2,5}    {2,3}                          {3,4}    {2,5}                          {3,5}    {2,6}                          {4,5}    {3,4}                          {3,4,5}  {3,5}                                   {4,5}                                   {4,6}                                   {5,6}                                   {2,5,6}                                   {3,4,5}                                   {4,5,6} MATHEMATICA Table[Length[Select[Subsets[Range[n]], Intersection[#, Union[Plus@@@Tuples[#, 2], Times@@@Tuples[#, 2]]]=={}&]], {n, 0, 10}] CROSSREFS Subsets without sums are A007865. Subsets without products are A326489. Subsets without differences or quotients are A326490. Maximal subsets without sums or products are A326497. Subsets with sums (and products) are A326083. Cf. A051026, A103580, A326020, A326076, A326117, A326491. Sequence in context: A004698 A014217 A034297 * A026636 A026658 A138688 Adjacent sequences:  A326492 A326493 A326494 * A326496 A326497 A326498 KEYWORD nonn AUTHOR Gus Wiseman, Jul 09 2019 EXTENSIONS Terms a(19) and beyond from Andrew Howroyd, Aug 25 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.

Last modified September 21 12:49 EDT 2020. Contains 337272 sequences. (Running on oeis4.)