cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-8 of 8 results.

A326489 Number of product-free subsets of {1..n}.

Original entry on oeis.org

1, 1, 2, 4, 6, 12, 22, 44, 88, 136, 252, 504, 896, 1792, 3392, 6352, 9720, 19440, 35664, 71328, 129952, 247232, 477664, 955328, 1700416, 2657280, 5184000, 10368000, 19407360, 38814720, 68868352, 137736704, 260693504, 505830400, 999641600, 1882820608, 2807196672
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Comments

A set is product-free if it contains no product of two (not necessarily distinct) elements.

Examples

			The a(0) = 1 through a(6) = 22 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}
                             {2,3,5}  {3,5}
                             {3,4,5}  {3,6}
                                      {4,5}
                                      {4,6}
                                      {5,6}
                                      {2,3,5}
                                      {2,5,6}
                                      {3,4,5}
                                      {3,4,6}
                                      {3,5,6}
                                      {4,5,6}
                                      {3,4,5,6}

Links

Crossrefs

Product-closed subsets are A326076.
Subsets containing no products are A326114.
Subsets containing no products of distinct elements are A326117.
Subsets containing no quotients are A327591.
Maximal product-free subsets are A326496.
Cf. A007865, A051026, A326023, A326081, A326116, A326495.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]],Intersection[#,Times@@@Tuples[#,2]]=={}&]],{n,10}]

Extensions

a(21)-a(36) from Andrew Howroyd, Aug 25 2019
a(0)=1 prepended to data, example and b-file by Peter Kagey, Sep 18 2019

A326496 Number of maximal product-free subsets of {1..n}.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 3, 3, 3, 4, 6, 6, 9, 9, 15, 17, 30, 30, 46, 46, 51, 61, 103, 103, 129, 158, 282, 282, 322, 322, 553, 553, 615, 689, 1247, 1365, 1870, 1870, 3566, 3758, 5244, 5244, 8677, 8677, 9807, 12147, 23351, 23351, 27469, 31694, 45718, 47186, 54594, 54594, 95382, 108198
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Comments

A set is product-free if it contains no product of two (not necessarily distinct) elements.
Also the number of maximal quotient-free subsets of {1..n}.

Examples

			The a(2) = 1 through a(10) = 6 subsets (A = 10):
  {2}  {23}  {23}  {235}  {235}   {2357}   {23578}   {23578}   {23578}
             {34}  {345}  {256}   {2567}   {25678}   {256789}  {2378A}
                          {3456}  {34567}  {345678}  {345678}  {256789}
                                                     {456789}  {26789A}
                                                               {345678A}
                                                               {456789A}

Links

Crossrefs

Product-free subsets are A326489.
Subsets without products of distinct elements are A326117.
Maximal sum-free subsets are A121269.
Maximal sum-free and product-free subsets are A326497.
Maximal subsets without products of distinct elements are A325710.
Cf. A007865, A051026, A326076, A326491, A326492, A326495, A327591.

Programs

  • Mathematica
    fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Times@@@Tuples[#,2]]=={}&]]],{n,0,10}]
  • PARI
    \\ See link for program file.
for(n=0, 30, print1(A326496(n), ", ")) \\ Andrew Howroyd, Aug 30 2019

Extensions

a(18)-a(55) from Andrew Howroyd, Aug 30 2019

A121269 Number of maximal sum-free subsets of {1,2,...,n}.

Original entry on oeis.org

1, 1, 2, 2, 4, 5, 6, 8, 13, 17, 23, 29, 37, 51, 66, 86, 118, 158, 201, 265, 359, 471, 598, 797, 1043, 1378, 1765, 2311, 3064, 3970, 5017, 6537, 8547, 11020, 14007, 18026, 23404, 30026, 37989, 48945, 62759, 80256, 101070, 129193, 164835, 209279, 262693, 334127
Offset: 0

Views

Author

N. Hindman (nhindman(AT)aol.com), Aug 23 2006

Keywords

Comments

Also the number of maximal subsets of {1..n} containing no differences of pairs of elements. - Gus Wiseman, Jul 10 2019

Examples

			a(5)=5 because the maximal sum-free subsets of {1,2,3,4,5} are {1,4}, {2,3}, {2,5}, {1,3,5} and {3,4,5}
From _Gus Wiseman_, Jul 10 2019: (Start)
The a(1) = 1 through a(8) = 13 subsets:
  {1}  {1}  {1,3}  {1,3}  {1,4}    {2,3}    {1,4,6}    {1,3,8}
       {2}  {2,3}  {1,4}  {2,3}    {1,3,5}  {1,4,7}    {1,4,6}
                   {2,3}  {2,5}    {1,4,6}  {2,3,7}    {1,4,7}
                   {3,4}  {1,3,5}  {2,5,6}  {2,5,6}    {1,5,8}
                          {3,4,5}  {3,4,5}  {2,6,7}    {1,6,8}
                                   {4,5,6}  {3,4,5}    {2,5,6}
                                            {1,3,5,7}  {2,5,8}
                                            {4,5,6,7}  {2,6,7}
                                                       {3,4,5}
                                                       {1,3,5,7}
                                                       {2,3,7,8}
                                                       {4,5,6,7}
                                                       {5,6,7,8}
(End)

Links

Crossrefs

Maximal product-free subsets are A326496.
Sum-free subsets are A007865.
Maximal sum-free and product-free subsets are A326497.
Subsets with sums are A326083.
Maximal subsets without sums of distinct elements are A326498.
Cf. A103580, A326020, A326489, A326495.

Programs

  • Mathematica
    fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Plus@@@Tuples[#,2]]=={}&]]],{n,0,10}] (* Gus Wiseman, Jul 10 2019 *)

Extensions

a(0) = 1 prepended by Gus Wiseman, Jul 10 2019
Terms a(42) and beyond from Fausto A. C. Cariboni, Oct 26 2020

A326497 Number of maximal sum-free and product-free subsets of {1..n}.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 4, 6, 8, 9, 15, 21, 26, 38, 51, 69, 89, 119, 149, 197, 261, 356, 447, 601, 781, 1003, 1293, 1714, 2228, 2931, 3697, 4843, 6258, 8187, 10273, 13445, 16894, 21953, 27469, 35842, 45410, 58948, 73939, 95199, 120593, 154510, 192995, 247966, 312642
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Comments

A set is sum-free and product-free if it contains no sum or product of two (not necessarily distinct) elements.

Examples

			The a(2) = 1 through a(10) = 15 subsets (A = 10):
  {2}  {23}  {23}  {23}   {23}   {237}   {256}   {267}    {23A}
             {34}  {25}   {256}  {256}   {258}   {345}    {345}
                   {345}  {345}  {267}   {267}   {357}    {34A}
                          {456}  {345}   {345}   {2378}   {357}
                                 {357}   {357}   {2569}   {38A}
                                 {4567}  {2378}  {2589}   {2378}
                                         {4567}  {4567}   {2569}
                                         {5678}  {4679}   {2589}
                                                 {56789}  {267A}
                                                          {269A}
                                                          {4567}
                                                          {4679}
                                                          {479A}
                                                          {56789}
                                                          {6789A}

Links

Crossrefs

Sum-free and product-free subsets are A326495.
Sum-free subsets are A007865.
Maximal sum-free subsets are A121269.
Product-free subsets are A326489.
Maximal product-free subsets are A326496.
Subsets with sums (and products) are A326083.
Cf. A051026, A103580, A325710, A326076, A326117, A326491, A326492, A326498.

Programs

  • Mathematica
    fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Union[Plus@@@Tuples[#,2],Times@@@Tuples[#,2]]]=={}&]]],{n,0,10}]
  • PARI
    \\ See link for program file.
for(n=0, 37, print1(A326497(n), ", ")) \\ Andrew Howroyd, Aug 30 2019

Extensions

a(21)-a(40) from Andrew Howroyd, Aug 30 2019
a(41)-a(48) from Jinyuan Wang, Oct 11 2020

A326490 Number of subsets of {1..n} containing no differences or quotients of pairs of distinct elements.

Original entry on oeis.org

1, 2, 3, 5, 7, 12, 18, 31, 46, 72, 102, 172, 259, 428, 607, 989, 1329, 2142, 3117, 4953, 6956, 11032, 15321, 23979, 33380, 48699, 66849, 104853, 144712, 220758, 304133, 461580, 636556, 973843, 1316513, 1958828, 2585433, 3882843, 5237093, 7884277, 10555739, 15729293
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Examples

			The a(0) = 1 through a(6) = 18 subsets:
  {}  {}   {}   {}     {}     {}       {}
      {1}  {1}  {1}    {1}    {1}      {1}
           {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}

Links

Crossrefs

Subsets without difference are A007865.
Maximal subsets without differences or quotients are A326491.
Subsets without quotients are A327591.
Subsets with differences and quotients are A326494.
Cf. A051026, A054519, A325860, A326023, A326079, A326489.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]],Intersection[#,Union[Divide@@@Reverse/@Subsets[#,{2}],Subtract@@@Reverse/@Subsets[#,{2}]]]=={}&]],{n,0,10}]
  • PARI
    a(n)={
   my(recurse(k, b)=
    if(k > n, 1,
      my(t = self()(k + 1, b));
      for(i=1, k\2, if(bittest(b,i) && (bittest(b,k-i) || (!(k%i) && bittest(b,k/i))), return(t)));
      t += self()(k + 1, b + (1<Andrew Howroyd, Aug 25 2019

Formula

For n > 0, a(n) = A326495(n) + 1.

Extensions

a(19)-a(41) from Andrew Howroyd, Aug 25 2019

A326498 Number of maximal subsets of {1..n} containing no sums of distinct elements.

Original entry on oeis.org

1, 1, 1, 3, 3, 6, 11, 16, 20, 32, 53, 78, 107, 149, 206, 292, 391, 556, 782, 1062, 1451, 1929, 2564, 3404, 4431, 5853, 7672, 9999, 12973, 16922, 22194, 28655, 36734, 47036, 60375, 76866, 97892, 123627, 157008, 196633, 248221, 311442, 390859, 488327, 610685
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Examples

			The a(1) = 1 through a(7) = 16 subsets:
  {1}  {1,2}  {1,2}  {1,3}    {1,2,4}  {1,2,4}    {1,2,4}
              {1,3}  {1,2,4}  {1,2,5}  {1,2,5}    {1,2,5}
              {2,3}  {2,3,4}  {1,3,5}  {1,2,6}    {1,2,6}
                              {2,3,4}  {1,3,5}    {1,2,7}
                              {2,4,5}  {1,3,6}    {1,3,6}
                              {3,4,5}  {1,4,6}    {1,4,6}
                                       {2,3,4}    {1,4,7}
                                       {2,3,6}    {2,3,4}
                                       {2,4,5}    {2,4,5}
                                       {2,5,6}    {2,4,7}
                                       {3,4,5,6}  {2,5,6}
                                                  {1,3,5,7}
                                                  {2,3,6,7}
                                                  {3,4,5,6}
                                                  {3,5,6,7}
                                                  {4,5,6,7}

Links

Crossrefs

Subsets without sums of distinct elements are A151897.
Maximal sum-free subsets are A121269.
Subsets with sums are A326083.
Maximal subsets without products of distinct elements are A325710.
Maximal subsets without sums or products of distinct elements are A326025.
Cf. A007865, A103580, A326117, A326495, A326497.

Programs

  • Mathematica
    fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Plus@@@Subsets[#,{2,n}]]=={}&]]],{n,0,10}]
  • PARI
    \\ See link for program file.
for(n=0, 25, print1(A326498(n), ", ")) \\ Andrew Howroyd, Aug 29 2019

Extensions

a(16)-a(40) from Andrew Howroyd, Aug 29 2019
a(41)-a(44) from Jinyuan Wang, Oct 11 2020

A326025 Number of maximal subsets of {1..n} containing no sums or products of distinct elements.

Original entry on oeis.org

1, 1, 2, 2, 2, 4, 5, 10, 13, 20, 28, 40, 54, 82, 120, 172, 244, 347, 471, 651, 874, 1198, 1635, 2210, 2867, 3895, 5234, 6889, 9019, 11919, 15629, 20460, 26254, 33827, 43881, 56367, 71841, 91834, 117695, 148503, 188039, 311442, 390859, 488327, 610685, 759665
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Examples

			The a(1) = 1 through a(8) = 13 maximal subsets:
  {1}  {1}  {1}    {1}      {1}      {1}        {1}        {1}
       {2}  {2,3}  {2,3,4}  {2,3,4}  {2,3,4}    {2,3,4}    {2,3,4}
                            {2,4,5}  {2,4,5}    {2,3,7}    {2,4,5}
                            {3,4,5}  {2,5,6}    {2,4,5}    {2,4,7}
                                     {3,4,5,6}  {2,4,7}    {2,5,6}
                                                {2,5,6}    {2,5,8}
                                                {2,6,7}    {2,6,7}
                                                {3,4,5,6}  {2,3,7,8}
                                                {3,5,6,7}  {3,4,5,6}
                                                {4,5,6,7}  {3,4,6,8}
                                                           {3,5,6,7}
                                                           {3,6,7,8}
                                                           {4,5,6,7,8}

Links

Crossrefs

Maximal subsets without sums of distinct elements are A326498.
Maximal subsets without products of distinct elements are A325710.
Subsets without sums or products of distinct elements are A326024.
Subsets with sums (and products) are A326083.
Maximal sum-free and product-free subsets are A326497.
Cf. A007865, A051026, A121269, A151897, A326116, A326117, A326491, A326495, A326496.

Programs

  • Mathematica
    fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Union[Plus@@@Subsets[#,{2,n}],Times@@@Subsets[#,{2,n}]]]=={}&]]],{n,0,10}]
  • PARI
    \\ See link for program file.
for(n=0, 25, print1(A326025(n), ", ")) \\ Andrew Howroyd, Aug 29 2019

Extensions

a(16)-a(40) from Andrew Howroyd, Aug 29 2019
a(41)-a(45) from Jinyuan Wang, Oct 03 2020

A326024 Number of subsets of {1..n} containing no sums or products of distinct elements.

Original entry on oeis.org

1, 2, 3, 5, 9, 15, 25, 41, 68, 109, 179, 284, 443, 681, 1062, 1587, 2440, 3638, 5443, 8021, 11953, 17273, 25578, 37001, 53953, 77429, 113063, 160636, 232928, 330775, 475380, 672056, 967831, 1359743, 1952235, 2743363, 3918401, 5495993, 7856134, 10984547, 15669741
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Examples

			The a(0) = 1 through a(5) = 15 subsets:
  {}  {}   {}   {}     {}       {}
      {1}  {1}  {1}    {1}      {1}
           {2}  {2}    {2}      {2}
                {3}    {3}      {3}
                {2,3}  {4}      {4}
                       {2,3}    {5}
                       {2,4}    {2,3}
                       {3,4}    {2,4}
                       {2,3,4}  {2,5}
                                {3,4}
                                {3,5}
                                {4,5}
                                {2,3,4}
                                {2,4,5}
                                {3,4,5}

Links

Crossrefs

Subsets without sums of distinct elements are A151897.
Subsets without products of distinct elements are A326117.
Maximal subsets without sums or products of distinct elements are A326025.
Subsets with sums (and products) are A326083.
Sum-free and product-free subsets are A326495.
Cf. A007865, A051026, A121269, A325710, A326076, A326489, A326497, A326498.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]],Intersection[#,Union[Plus@@@Subsets[#,{2,n}],Times@@@Subsets[#,{2,n}]]]=={}&]],{n,0,10}]
  • PARI
    a(n)={
   my(recurse(k, es, ep)=
    if(k > n, 1,
      my(t = self()(k + 1, es, ep));
      if(!bittest(es,k) && !bittest(ep,k),
         es = bitor(es, bitand((2<Andrew Howroyd, Aug 25 2019

Extensions

Terms a(16)-a(40) from Andrew Howroyd, Aug 25 2019
Showing 1-8 of 8 results.

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