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.

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A365006 Number of strict integer partitions of n such that no part can be written as a (strictly) positive linear combination of the others.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 3, 2, 4, 4, 8, 4, 11, 9, 16, 14, 25, 20, 37, 31, 49, 47, 73, 64, 101, 96, 135, 133, 190, 181, 256, 253, 336, 342, 453, 452, 596, 609, 771, 803, 1014, 1041, 1309, 1362, 1674, 1760, 2151, 2249, 2736, 2884, 3449, 3661, 4366, 4615, 5486, 5825
Offset: 0

Views

Author

Gus Wiseman, Aug 31 2023

Keywords

Comments

We consider (for example) that 2x + y + 3z is a positive linear combination of (x,y,z), but 2x + y is not, as the coefficient of z is 0.

Examples

			The a(8) = 2 through a(13) = 11 partitions:
  (8)    (9)      (10)       (11)       (12)       (13)
  (5,3)  (5,4)    (6,4)      (6,5)      (7,5)      (7,6)
         (7,2)    (7,3)      (7,4)      (5,4,3)    (8,5)
         (4,3,2)  (4,3,2,1)  (8,3)      (5,4,2,1)  (9,4)
                             (9,2)                 (10,3)
                             (5,4,2)               (11,2)
                             (6,3,2)               (6,4,3)
                             (5,3,2,1)             (6,5,2)
                                                   (7,4,2)
                                                   (5,4,3,1)
                                                   (6,4,2,1)
		

Crossrefs

The nonnegative version for subsets appears to be A124506.
For sums instead of combinations we have A364349, binary A364533.
The nonnegative version is A364350, complement A364839.
For subsets instead of partitions we have A365044, complement A365043.
The non-strict version is A365072, nonnegative A364915.
A000041 counts integer partitions, strict A000009.
A008284 counts partitions by length, strict A008289.
A116861 and A364916 count linear combinations of strict partitions.
A364912 counts linear combinations of partitions of k.

Programs

  • Mathematica
    combp[n_,y_]:=With[{s=Table[{k,i},{k,y},{i,1,Floor[n/k]}]},Select[Tuples[s],Total[Times@@@#]==n&]];
    Table[Length[Select[IntegerPartitions[n],UnsameQ@@#&&And@@Table[combp[#[[k]],Delete[#,k]]=={},{k,Length[#]}]&]],{n,0,30}]
  • Python
    from sympy.utilities.iterables import partitions
    def A365006(n):
        if n <= 1: return 1
        alist = [set(tuple(sorted(set(p))) for p in partitions(i)) for i in range(n)]
        c = 1
        for p in partitions(n,k=n-1):
            if max(p.values()) == 1:
                s = set(p)
                for q in s:
                    if tuple(sorted(s-{q})) in alist[q]:
                        break
                else:
                    c += 1
        return c # Chai Wah Wu, Sep 20 2023

Extensions

a(31)-a(56) from Chai Wah Wu, Sep 20 2023

A365044 Number of subsets of {1..n} whose greatest element cannot be written as a (strictly) positive linear combination of the others.

Original entry on oeis.org

1, 2, 3, 5, 9, 20, 43, 96, 207, 442, 925, 1913, 3911, 7947, 16061, 32350, 64995, 130384, 261271, 523194, 1047208, 2095459, 4192212, 8386044, 16774078, 33550622, 67104244, 134212163, 268428760, 536862900, 1073732255, 2147472267, 4294953778, 8589918612, 17179850312
Offset: 0

Views

Author

Gus Wiseman, Aug 26 2023

Keywords

Comments

Sets of this type may be called "positive combination-free".
Also subsets of {1..n} such that no element can be written as a (strictly) positive linear combination of the others.

Examples

			The subset S = {3,5,6,8} has 6 = 2*3 + 0*5 + 0*8 and 8 = 1*3 + 1*5 + 0*6 but neither of these is strictly positive, so S is counted under a(8).
The a(0) = 1 through a(5) = 20 subsets:
  {}  {}   {}   {}     {}         {}
      {1}  {1}  {1}    {1}        {1}
           {2}  {2}    {2}        {2}
                {3}    {3}        {3}
                {2,3}  {4}        {4}
                       {2,3}      {5}
                       {3,4}      {2,3}
                       {2,3,4}    {2,5}
                       {1,2,3,4}  {3,4}
                                  {3,5}
                                  {4,5}
                                  {2,3,4}
                                  {2,4,5}
                                  {3,4,5}
                                  {1,2,3,4}
                                  {1,2,3,5}
                                  {1,2,4,5}
                                  {1,3,4,5}
                                  {2,3,4,5}
                                  {1,2,3,4,5}
		

Crossrefs

The binary version is A007865, first differences A288728.
The binary complement is A093971, first differences A365070.
Without re-usable parts we have A151897, first differences A365071.
The nonnegative version is A326083, first differences A124506.
A subclass is A341507.
The nonnegative complement is A364914, first differences A365046.
The complement is counted by A365043, first differences A365042.
First differences are A365045.
A085489 and A364755 count subsets w/o the sum of two distinct elements.
A088809 and A364756 count subsets with the sum of two distinct elements.
A364350 counts combination-free strict partitions, complement A364839.
A364913 counts combination-full partitions.

Programs

  • Mathematica
    combp[n_,y_]:=With[{s=Table[{k,i},{k,y},{i,1,Floor[n/k]}]},Select[Tuples[s],Total[Times@@@#]==n&]];
    Table[Length[Select[Subsets[Range[n]],And@@Table[combp[Last[#],Union[Most[#]]]=={},{k,Length[#]}]&]],{n,0,10}]
  • Python
    from itertools import combinations
    from sympy.utilities.iterables import partitions
    def A365044(n):
        mlist = tuple({tuple(sorted(p.keys())) for p in partitions(m,k=m-1)} for m in range(1,n+1))
        return n+1+sum(1 for k in range(2,n+1) for w in combinations(range(1,n+1),k) if w[:-1] not in mlist[w[-1]-1]) # Chai Wah Wu, Nov 20 2023

Formula

a(n) = 2^n - A365043(n).

Extensions

a(15)-a(34) from Chai Wah Wu, Nov 20 2023

A365042 Number of subsets of {1..n} containing n such that some element can be written as a positive linear combination of the others.

Original entry on oeis.org

0, 0, 1, 2, 4, 5, 9, 11, 17, 21, 29, 36, 50, 60, 78, 95, 123, 147, 185, 221, 274, 325, 399, 472, 574, 672, 810, 945, 1131, 1316, 1557, 1812, 2137, 2462, 2892, 3322, 3881, 4460, 5176, 5916, 6846, 7817, 8993, 10250, 11765, 13333, 15280, 17308, 19731, 22306
Offset: 0

Views

Author

Gus Wiseman, Aug 23 2023

Keywords

Comments

Sets of this type may be called "positive combination-full".
Also subsets of {1..n} containing n whose greatest element can be written as a positive linear combination of the others.

Examples

			The subset {3,4,10} has 10 = 2*3 + 1*4 so is counted under a(10).
The a(0) = 0 through a(7) = 11 subsets:
  .  .  {1,2}  {1,3}    {1,4}    {1,5}    {1,6}      {1,7}
               {1,2,3}  {2,4}    {1,2,5}  {2,6}      {1,2,7}
                        {1,2,4}  {1,3,5}  {3,6}      {1,3,7}
                        {1,3,4}  {1,4,5}  {1,2,6}    {1,4,7}
                                 {2,3,5}  {1,3,6}    {1,5,7}
                                          {1,4,6}    {1,6,7}
                                          {1,5,6}    {2,3,7}
                                          {2,4,6}    {2,5,7}
                                          {1,2,3,6}  {3,4,7}
                                                     {1,2,3,7}
                                                     {1,2,4,7}
		

Crossrefs

The nonnegative complement is A124506, first differences of A326083.
The binary complement is A288728, first differences of A007865.
First differences of A365043.
The complement is counted by A365045, first differences of A365044.
The nonnegative version is A365046, first differences of A364914.
Without re-usable parts we have A365069, first differences of A364534.
The binary version is A365070, first differences of A093971.
A085489 and A364755 count subsets with no sum of two distinct elements.
A088314 counts sets that can be linearly combined to obtain n.
A088809 and A364756 count subsets with some sum of two distinct elements.
A364350 counts combination-free strict partitions, complement A364839.
A364913 counts combination-full partitions.

Programs

  • Mathematica
    combp[n_,y_]:=With[{s=Table[{k,i},{k,y},{i,1,Floor[n/k]}]},Select[Tuples[s],Total[Times@@@#]==n&]];
    Table[Length[Select[Subsets[Range[n]],MemberQ[#,n]&&Or@@Table[combp[#[[k]],Union[Delete[#,k]]]!={},{k,Length[#]}]&]],{n,0,10}]

Formula

a(n) = A088314(n) - 1.

A365070 Number of subsets of {1..n} containing n and some element equal to the sum of two other (possibly equal) elements.

Original entry on oeis.org

0, 0, 1, 1, 5, 9, 24, 46, 109, 209, 469, 922, 1932, 3858, 7952, 15831, 32214, 64351, 129813, 259566, 521681, 1042703, 2091626, 4182470, 8376007, 16752524, 33530042, 67055129, 134165194, 268328011, 536763582, 1073523097, 2147268041, 4294505929, 8589506814, 17178978145
Offset: 0

Views

Author

Gus Wiseman, Aug 24 2023

Keywords

Comments

These are binary sum-full sets where elements can be re-used. The complement is counted by A288728. The non-binary version is A365046, complement A124506. For non-re-usable parts we have A364756, complement A085489.

Examples

			The subset {1,3} has no element equal to the sum of two others, so is not counted under a(3).
The subset {3,4,5} has no element equal to the sum of two others, so is not counted under a(5).
The subset {1,3,4} has 4 = 1 + 3, so is counted under a(4).
The subset {2,4,5} has 4 = 2 + 2, so is counted under a(5).
The a(0) = 0 through a(5) = 9 subsets:
  .  .  {1,2}  {1,2,3}  {2,4}      {1,2,5}
                        {1,2,4}    {1,4,5}
                        {1,3,4}    {2,3,5}
                        {2,3,4}    {2,4,5}
                        {1,2,3,4}  {1,2,3,5}
                                   {1,2,4,5}
                                   {1,3,4,5}
                                   {2,3,4,5}
                                   {1,2,3,4,5}
		

Crossrefs

The complement w/o re-usable parts is A085489, first differences of A364755.
First differences of A093971.
The non-binary complement is A124506, first differences of A326083.
The complement is counted by A288728, first differences of A007865.
For partitions (not requiring n) we have A363225, strict A363226.
The case without re-usable parts is A364756, firsts differences of A088809.
The non-binary version is A365046, first differences of A364914.
A116861 and A364916 count linear combinations of strict partitions.
A364350 counts combination-free strict partitions, complement A364839.
A364913 counts combination-full partitions.
A365006 counts no positive combination-full strict ptns.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]], MemberQ[#,n]&&Intersection[#,Total /@ Tuples[#,2]]!={}&]], {n,0,10}]

Formula

First differences of A093971.

Extensions

a(21) onwards added (using A093971) by Andrew Howroyd, Jan 13 2024

A364671 Number of subsets of {1..n} containing all of their own first differences.

Original entry on oeis.org

1, 2, 4, 6, 10, 14, 23, 34, 58, 96, 171, 302, 565, 1041, 1969, 3719, 7105, 13544, 25999, 49852, 95949, 184658, 356129, 687068, 1327540, 2566295, 4966449, 9617306, 18640098, 36150918, 70166056, 136272548, 264844111, 515036040, 1002211421, 1951345157, 3801569113
Offset: 0

Views

Author

Gus Wiseman, Aug 04 2023

Keywords

Examples

			The subset {1,2,4,5,10,14} has differences (1,2,1,5,4) so is counted under a(14).
The a(0) = 1 through a(5) = 14 subsets:
  {}  {}   {}     {}       {}         {}
      {1}  {1}    {1}      {1}        {1}
           {2}    {2}      {2}        {2}
           {1,2}  {3}      {3}        {3}
                  {1,2}    {4}        {4}
                  {1,2,3}  {1,2}      {5}
                           {2,4}      {1,2}
                           {1,2,3}    {2,4}
                           {1,2,4}    {1,2,3}
                           {1,2,3,4}  {1,2,4}
                                      {1,2,3,4}
                                      {1,2,3,5}
                                      {1,2,4,5}
                                      {1,2,3,4,5}
		

Crossrefs

For differences of all strict pairs we have A054519, for partitions A007862.
For "disjoint" instead of "subset" we have A364463, partitions A363260.
For "non-disjoint" we have A364466, partitions A364467 (strict A364536).
The complement is counted by A364672, partitions A364673, A364674, A364675.
First differences of terms are A364752, complement A364753.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]], SubsetQ[#,Differences[#]]&]], {n,0,10}]

Extensions

More terms from Rémy Sigrist, Aug 06 2023

A365069 Number of subsets of {1..n} containing n and some element equal to the sum of two or more distinct other elements. A variation of non-binary sum-full subsets without re-usable elements.

Original entry on oeis.org

0, 0, 0, 1, 2, 7, 17, 41, 88, 201, 418, 892, 1838, 3798, 7716, 15740
Offset: 0

Views

Author

Gus Wiseman, Aug 26 2023

Keywords

Comments

The complement is counted by A365071. The binary case is A364756. Allowing elements to be re-used gives A365070. A version for partitions (but not requiring n) is A237668.

Examples

			The subset {2,4,6} has 6 = 4 + 2 so is counted under a(6).
The subset {1,2,4,7} has 7 = 4 + 2 + 1 so is counted under a(7).
The subset {1,4,5,8} has 5 = 4 + 1 so is counted under a(8).
The a(0) = 0 through a(6) = 17 subsets:
  .  .  .  {1,2,3}  {1,3,4}    {1,4,5}      {1,5,6}
                    {1,2,3,4}  {2,3,5}      {2,4,6}
                               {1,2,3,5}    {1,2,3,6}
                               {1,2,4,5}    {1,2,4,6}
                               {1,3,4,5}    {1,2,5,6}
                               {2,3,4,5}    {1,3,4,6}
                               {1,2,3,4,5}  {1,3,5,6}
                                            {1,4,5,6}
                                            {2,3,4,6}
                                            {2,3,5,6}
                                            {2,4,5,6}
                                            {1,2,3,4,6}
                                            {1,2,3,5,6}
                                            {1,2,4,5,6}
                                            {1,3,4,5,6}
                                            {2,3,4,5,6}
                                            {1,2,3,4,5,6}
		

Crossrefs

The complement w/ re-usable parts is A288728, first differences of A007865.
First differences of A364534.
The binary complement is A364755, first differences of A085489.
The binary version is A364756, first differences of A088809.
The version with re-usable parts is A365070, first differences of A093971.
The complement is counted by A365071, first differences of A151897.
A124506 counts nonnegative combination-free subsets, differences of A326083.
A365046 counts nonnegative combination-full subsets, differences of A364914.
Strict partitions: A116861, A364272, A364349, A364350, A364839, A364916.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]], MemberQ[#,n]&&Intersection[#, Total/@Subsets[#, {2,Length[#]}]]!={}&]],{n,0,10}]

Formula

a(n) = 2^(n-1) - A365070(n).
First differences of A364534.

A325710 Number of maximal subsets of {1..n} containing no products of distinct elements.

Original entry on oeis.org

1, 1, 2, 2, 2, 2, 4, 4, 6, 6, 10, 10, 14, 14, 24, 28, 32, 32, 62, 62, 92, 102, 184, 184, 254, 254, 474, 506, 686, 686, 1172, 1172, 1792, 1906, 3568, 3794, 5326, 5326, 10282, 10618, 14822, 14822, 25564, 25564, 35304, 39432, 76888, 76888, 100574, 100574, 197870, 201622, 282014
Offset: 0

Views

Author

Gus Wiseman, Jul 09 2019

Keywords

Examples

			The a(1) = 1 through a(9) = 6 maximal subsets:
  {1}  {1}  {1}   {1}    {1}     {1}     {1}      {1}       {1}
       {2}  {23}  {234}  {2345}  {2345}  {23457}  {23457}   {234579}
                                 {2456}  {24567}  {23578}   {235789}
                                 {3456}  {34567}  {24567}   {245679}
                                                  {25678}   {256789}
                                                  {345678}  {3456789}
		

Crossrefs

Subsets without products of distinct elements are A326117.
Maximal product-free subsets are A326496.
Subsets with products are A326076.
Maximal subsets without sums of distinct elements are A326498.
Maximal subsets without quotients are A326492.
Maximal subsets without sums or products of distinct elements are A326025.

Programs

  • Mathematica
    fasmax[y_]:=Complement[y,Union@@(Most[Subsets[#]]&/@y)];
    Table[Length[fasmax[Select[Subsets[Range[n]],Intersection[#,Times@@@Subsets[#,{2,n}]]=={}&]]],{n,0,10}]
  • PARI
    \\ See link for program file.
    for(n=0, 30, print1(A325710(n), ", ")) \\ Andrew Howroyd, Aug 29 2019

Extensions

Terms a(16) and beyond from Andrew Howroyd, Aug 29 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}
		

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.

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

A364672 Number of subsets of {1..n} not containing all of their own first differences.

Original entry on oeis.org

0, 0, 0, 2, 6, 18, 41, 94, 198, 416, 853, 1746, 3531, 7151, 14415, 29049, 58431, 117528, 236145, 474436, 952627, 1912494, 3838175, 7701540, 15449676, 30988137, 62142415, 124600422, 249795358, 500719994, 1003575768, 2011211100, 4030123185, 8074898552, 16177657763, 32408393211, 64917907623
Offset: 0

Views

Author

Gus Wiseman, Aug 05 2023

Keywords

Examples

			The a(0) = 0 through a(5) = 18 subsets:
  .  .  .  {1,3}  {1,3}    {1,3}
           {2,3}  {1,4}    {1,4}
                  {2,3}    {1,5}
                  {3,4}    {2,3}
                  {1,3,4}  {2,5}
                  {2,3,4}  {3,4}
                           {3,5}
                           {4,5}
                           {1,2,5}
                           {1,3,4}
                           {1,3,5}
                           {1,4,5}
                           {2,3,4}
                           {2,3,5}
                           {2,4,5}
                           {3,4,5}
                           {1,3,4,5}
                           {2,3,4,5}
		

Crossrefs

For disjunction instead of containment we have A364463, partitions A363260.
For overlap we have A364466, partitions A364467 (strict A364536).
The complement is counted by A364671, partitions A364673, A364674, A364675.
First differences of terms are A364753, complement A364752.

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n]],!SubsetQ[#,Differences[#]]&]],{n,0,10}]

Formula

a(n) = 2^n - A364671(n). - Andrew Howroyd, Jan 27 2024

Extensions

a(21) onwards (using A364671) added by Andrew Howroyd, Jan 27 2024

A365068 Number of integer partitions of n with some part that can be written as a nonnegative linear combination of the other distinct parts.

Original entry on oeis.org

0, 0, 0, 1, 2, 4, 7, 10, 16, 23, 34, 44, 67, 85, 119, 157, 210, 268, 360, 453, 592, 748, 956, 1195, 1520, 1883, 2365, 2920, 3628, 4451, 5494, 6702, 8211, 9976, 12147, 14666, 17776, 21389, 25774, 30887, 37035, 44224, 52819, 62836, 74753, 88614, 105062, 124160
Offset: 0

Views

Author

Gus Wiseman, Aug 27 2023

Keywords

Comments

These may be called "non-binary nonnegative combination-full" partitions.
Does not necessarily include all non-strict partitions (A047967).

Examples

			The partition (5,4,3,3) has no part that can be written as a nonnegative linear combination of the others, so is not counted under a(15).
The partition (6,4,3,2) has 6 = 1*2 + 1*4, so is counted under a(15). The combinations 6 = 2*3 = 3*2 and 4 = 2*2 can also be used.
The a(3) = 1 through a(8) = 16 partitions:
  (21)  (31)   (41)    (42)     (61)      (62)
        (211)  (221)   (51)     (331)     (71)
               (311)   (321)    (421)     (422)
               (2111)  (411)    (511)     (431)
                       (2211)   (2221)    (521)
                       (3111)   (3211)    (611)
                       (21111)  (4111)    (3221)
                                (22111)   (3311)
                                (31111)   (4211)
                                (211111)  (5111)
                                          (22211)
                                          (32111)
                                          (41111)
                                          (221111)
                                          (311111)
                                          (2111111)
		

Crossrefs

The complement for sums instead of combinations is A237667, binary A236912.
For sums instead of combinations we have A237668, binary A237113.
The strict case is A364839, complement A364350.
Allowing equal parts in the combination gives A364913.
For subsets instead of partitions we have A364914, complement A326083.
The complement is A364915.
A000041 counts integer partitions, strict A000009.
A008284 counts partitions by length, strict A008289.
A116861 and A364916 count linear combinations of strict partitions.
A323092 counts double-free partitions, ranks A320340.
A364912 counts linear combinations of partitions of k.

Programs

  • Mathematica
    combs[n_,y_]:=With[{s=Table[{k,i},{k,y},{i,0,Floor[n/k]}]}, Select[Tuples[s],Total[Times@@@#]==n&]];
    Table[Length[Select[IntegerPartitions[n], Function[ptn,Or@@Table[combs[ptn[[k]], DeleteCases[ptn,ptn[[k]]]]!={}, {k,Length[ptn]}]]]],{n,0,5}]
  • Python
    from sympy.utilities.iterables import partitions
    def A365068(n):
        if n <= 1: return 0
        alist, c = [set(tuple(sorted(set(p))) for p in partitions(i)) for i in range(n)], 0
        for p in partitions(n,k=n-1):
            s = set(p)
            if any(set(t).issubset(s-{q}) for q in s for t in alist[q]):
                c += 1
        return c # Chai Wah Wu, Sep 20 2023

Extensions

a(31)-a(47) from Chai Wah Wu, Sep 20 2023
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