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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A353854 Length of the trajectory of the composition run-sum transformation (condensation) of the n-th composition in standard order.

Original entry on oeis.org

1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 2, 3, 1, 1, 3, 2, 1, 1, 1, 2, 1, 2, 1, 2, 1, 1, 2, 3, 2, 3, 2, 2, 1, 1, 1, 2, 2, 1, 1, 3, 1, 1, 2, 2, 1, 1, 3, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 2, 2, 3, 3, 2, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 2, 3, 1, 1, 3, 2, 1, 1, 1, 2, 2, 2, 2
Offset: 0

Views

Author

Gus Wiseman, Jun 01 2022

Keywords

Comments

Every sequence can be uniquely split into a sequence of non-overlapping runs. For example, the runs of (2,2,1,1,1,3,2,2) are ((2,2),(1,1,1),(3),(2,2)), with sums (4,3,3,4). The run-sum trajectory is obtained by repeatedly taking the run-sum transformation (A353847) until the rank of an anti-run is reached. For example, the trajectory 11 -> 10 -> 8 corresponds to the trajectory (2,1,1) -> (2,2) -> (4), with length a(11) = 3.
The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.

Examples

			The trajectory of 94685 and the a(94685) = 5 corresponding compositions:
  94685: (2,1,1,4,1,1,2,1,1,2,1)
  86357: (2,2,4,2,2,2,2,1)
  69889: (4,4,8,1)
  65793: (8,8,1)
  65537: (16,1)

Crossrefs

Positions of first appearances are A072639.
Positions of 1's are A333489, counted by A003242 (complement A261983).
The version for partitions is A353841.
The last part of the same trajectory is A353855.
This is the rank statistic counted by A353859.
A005811 counts runs in binary expansion.
A011782 counts compositions.
A066099 lists compositions in standard order.
A318928 gives runs-resistance of binary expansion.
A333627 represents the run-lengths of standard compositions.
A353832 represents the run-sum transformation of a partition.
A353840-A353846 pertain to the partition run-sum trajectory.
A353847 represents the run-sum transformation of a composition.
A353853-A353859 pertain to the composition run-sum trajectory.
A353932 lists run-sums of standard compositions, represented by A353847.
Cf. A237685, A238279, A304442, A325277, A333755, A353848, A353849, A353850, A353852, A353860.

Programs

  • Mathematica
    stc[n_]:=Differences[Prepend[Join@@ Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
Table[Length[FixedPointList[Total/@Split[#]&,stc[n]]]-1,{n,0,100}]

A353855 Last term of the trajectory of the composition run-sum transformation (condensation) of the n-th composition in standard order.

Original entry on oeis.org

0, 1, 2, 2, 4, 5, 6, 4, 8, 9, 8, 8, 12, 13, 8, 8, 16, 17, 18, 18, 20, 17, 22, 20, 24, 25, 24, 24, 20, 17, 18, 16, 32, 33, 34, 34, 32, 37, 38, 32, 40, 41, 32, 34, 44, 45, 32, 40, 48, 49, 50, 50, 52, 49, 54, 52, 40, 41, 40, 32, 32, 37, 34, 32, 64, 65, 66, 66, 68
Offset: 0

Views

Author

Gus Wiseman, Jun 01 2022

Keywords

Comments

Every sequence can be uniquely split into a sequence of non-overlapping runs. For example, the runs of (2,2,1,1,1,3,2,2) are ((2,2),(1,1,1),(3),(2,2)), with sums (4,3,3,4). The run-sum trajectory is obtained by repeatedly taking the run-sum transformation (A353847) until the rank of an anti-run is reached. For example, the trajectory 11 -> 10 -> 8, corresponding to (2,1,1) -> (2,2) -> (4), has last term a(11) = 8.
The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.

Examples

			The trajectory 139 -> 138 -> 136 -> 128 ends with a(139) = 128.

Crossrefs

The version for partitions is A353842.
This trajectory has length A353854, firsts A072639, partitions A353841.
A005811 counts runs in binary expansion.
A011782 counts compositions.
A066099 lists compositions in standard order.
A318928 gives runs-resistance of binary expansion.
A325268 counts partitions by omicron, rank statistic A304465.
A333627 ranks the run-lengths of standard compositions.
A351014 counts distinct runs in standard compositions, firsts A351015.
A353840-A353846 pertain to a partition's run-sum trajectory.
A353847 represents a composition's run-sums, partitions A353832.
A353853-A353859 pertain to a composition's run-sum trajectory.
Cf. A237685, A304442, A333381, A333489, A333755, A353848, A353849, A353850, A353852, A353860.

Programs

  • Mathematica
    stc[n_]:=Differences[Prepend[Join@@ Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
Table[Total[2^Accumulate[Reverse[FixedPoint[Total/@Split[#]&,stc[n]]]]/2],{n,0,100}]

A353858 Number of integer compositions of n with run-sum trajectory ending in a singleton.

Original entry on oeis.org

0, 1, 2, 2, 5, 2, 8, 2, 20, 5, 8, 2, 78, 2, 8, 8, 223, 2, 179, 2, 142, 8, 8, 2, 4808
Offset: 0

Views

Author

Gus Wiseman, Jun 17 2022

Keywords

Comments

Every sequence can be uniquely split into a sequence of non-overlapping runs. For example, the runs of (2,2,1,1,1,3,2,2) are ((2,2),(1,1,1),(3),(2,2)), with sums (4,3,3,4). The run-sum trajectory is obtained by repeatedly taking the run-sums (cf. A353847) until an anti-run composition (A003242) is reached. For example, the composition (2,2,1,1,2) is counted under a(8) because it has the following run-sum trajectory: (2,2,1,1,2) -> (4,2,2) -> (4,4) -> (8).

Examples

			The a(0) = 0 through a(8) = 20 compositions:
  .  (1)  (2)   (3)    (4)     (5)      (6)       (7)        (8)
          (11)  (111)  (22)    (11111)  (33)      (1111111)  (44)
                       (112)            (222)                (224)
                       (211)            (1113)               (422)
                       (1111)           (2112)               (1124)
                                        (3111)               (2114)
                                        (11211)              (2222)
                                        (111111)             (4112)
                                                             (4211)
                                                             (11114)
                                                             (21122)
                                                             (22112)
                                                             (41111)
                                                             (111122)
                                                             (112112)
                                                             (211211)
                                                             (221111)
                                                             (1111211)
                                                             (1121111)
                                                             (11111111)

Crossrefs

The version for partitions is A353845, ranked by A353844.
The trajectory itself is A353853, last part A353855.
The lengths of trajectories of standard compositions are A353854.
This is column k = 1 of A353856, for partitions A353843.
These compositions are ranked by A353857.
A011782 counts compositions.
A066099 lists compositions in standard order.
A238279 and A333755 count compositions by number of runs.
A275870 counts collapsible partitions, ranked by A300273.
A333489 ranks anti-runs, counted by A003242 (complement A261983).
A353840-A353846 pertain to partition run-sum trajectory.
A353847 represents the run-sums of a composition, partitions A353832.
A353851 counts compositions with equal run-sums, ranked by A353848.
A353859 counts compositions by length of run-sum trajectory.
A353860 counts collapsible compositions.
A353932 lists run-sums of standard compositions.
Cf. A072639, A237685, A304442, A304465, A318928, A353833, A353841, A353849, A353850, A353852.

Programs

  • Mathematica
    Table[Length[Select[Join@@Permutations/@ IntegerPartitions[n], Length[FixedPoint[Total/@Split[#]&,#]]==1&]],{n,0,15}]

A368184 Least k such that there are exactly n ways to choose a set consisting of a different binary index of each binary index of k.

Original entry on oeis.org

7, 1, 4, 20, 276, 320, 1088, 65856, 66112, 66624, 263232
Offset: 0

Views

Author

Gus Wiseman, Dec 18 2023

Keywords

Comments

A binary index of n (row n of A048793) is any position of a 1 in its reversed binary expansion. For example, 18 has reversed binary expansion (0,1,0,0,1) and binary indices {2,5}.

Examples

			The terms together with the corresponding set-systems begin:
      7: {{1},{2},{1,2}}
      1: {{1}}
      4: {{1,2}}
     20: {{1,2},{1,3}}
    276: {{1,2},{1,3},{1,4}}
    320: {{1,2,3},{1,4}}
   1088: {{1,2,3},{1,2,4}}
  65856: {{1,2,3},{1,4},{1,5}}
  66112: {{1,2,3},{2,4},{1,5}}
  66624: {{1,2,3},{1,2,4},{1,5}}

Crossrefs

For strict sequences: A367910, firsts of A367905, sorted A367911.
For multisets w/o distinctness: A367913, firsts of A367912, sorted A367915.
For sequences w/o distinctness: A368111, firsts of A368109, sorted A368112.
Positions of first appearances in A368183.
The sorted version is A368185.
A048793 lists binary indices, length A000120, sum A029931.
A058891 counts set-systems, covering A003465, connected A323818.
A070939 gives length of binary expansion.
A096111 gives product of binary indices.
Cf. A072639, A253317, A326031, A326702, A326753, A355739, A355741, A367771, A367906, A367907.

Programs

  • Mathematica
    nn=10000;
bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
q=Table[Length[Union[Sort/@Select[Tuples[bpe/@bpe[n]], UnsameQ@@#&]]],{n,nn}];
k=Max@@Select[Range[Max@@q], SubsetQ[q,Range[#]]&]
Table[Position[q,n][[1,1]],{n,0,k}]

A368185 Sorted list of positions of first appearances in A368183 (number of sets that can be obtained by choosing a different binary index of each binary index).

Original entry on oeis.org

1, 4, 7, 20, 276, 320, 1088, 65856, 66112, 66624
Offset: 1

Views

Author

Gus Wiseman, Dec 18 2023

Keywords

Comments

A binary index of n (row n of A048793) is any position of a 1 in its reversed binary expansion. For example, 18 has reversed binary expansion (0,1,0,0,1) and binary indices {2,5}.

Examples

			The terms together with the corresponding set-systems begin:
      1: {{1}}
      4: {{1,2}}
      7: {{1},{2},{1,2}}
     20: {{1,2},{1,3}}
    276: {{1,2},{1,3},{1,4}}
    320: {{1,2,3},{1,4}}
   1088: {{1,2,3},{1,2,4}}
  65856: {{1,2,3},{1,4},{1,5}}
  66112: {{1,2,3},{2,4},{1,5}}
  66624: {{1,2,3},{1,2,4},{1,5}}

Crossrefs

For sequences we have A367911, unsorted A367910, firsts of A367905.
Multisets w/o distinctness: A367915, unsorted A367913, firsts of A367912.
Sequences w/o distinctness: A368112, unsorted A368111, firsts of A368109.
Sorted list of positions of first appearances in A368183.
The unsorted version is A368184.
A048793 lists binary indices, length A000120, sum A029931.
A058891 counts set-systems, covering A003465, connected A323818.
A070939 gives length of binary expansion.
A096111 gives product of binary indices.
Cf. A072639, A253317, A326031, A326702, A326753, A355739, A355741, A367771, A367906, A367907.

Programs

  • Mathematica
    bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
c=Table[Length[Union[Sort/@Select[Tuples[bpe/@bpe[n]], UnsameQ@@#&]]],{n,1000}];
Select[Range[Length[c]], FreeQ[Take[c,#-1],c[[#]]]&]

A370644 Number of minimal subsets of {2..n} such that it is not possible to choose a different binary index of each element.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 4, 13, 13, 26, 56, 126, 243, 471, 812, 1438
Offset: 0

Views

Author

Gus Wiseman, Mar 11 2024

Keywords

Comments

A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793.

Examples

			The a(0) = 0 through a(7) = 13 subsets:
  .  .  .  .  .  {2,3,4,5}  {2,4,6}    {2,4,6}
                            {2,3,4,5}  {2,3,4,5}
                            {2,3,5,6}  {2,3,4,7}
                            {3,4,5,6}  {2,3,5,6}
                                       {2,3,5,7}
                                       {2,3,6,7}
                                       {2,4,5,7}
                                       {2,5,6,7}
                                       {3,4,5,6}
                                       {3,4,5,7}
                                       {3,4,6,7}
                                       {3,5,6,7}
                                       {4,5,6,7}
The a(0) = 0 through a(7) = 13 set-systems:
  .  .  .  .  .  {2}{12}{3}{13}  {2}{3}{23}       {2}{3}{23}
                                 {2}{12}{3}{13}   {2}{12}{3}{13}
                                 {12}{3}{13}{23}  {12}{3}{13}{23}
                                 {2}{12}{13}{23}  {2}{12}{13}{23}
                                                  {2}{12}{3}{123}
                                                  {2}{3}{13}{123}
                                                  {12}{3}{13}{123}
                                                  {12}{3}{23}{123}
                                                  {2}{12}{13}{123}
                                                  {2}{12}{23}{123}
                                                  {2}{13}{23}{123}
                                                  {3}{13}{23}{123}
                                                  {12}{13}{23}{123}

Crossrefs

The version with ones allowed is A370642, minimal case of A370637.
This is the minimal case of A370643.
A048793 lists binary indices, A000120 length, A272020 reverse, A029931 sum.
A070939 gives length of binary expansion.
A096111 gives product of binary indices.
A367902 counts choosable set-systems, ranks A367906, unlabeled A368095.
A367903 counts non-choosable set-systems, ranks A367907, unlabeled A368094.
A370585 counts maximal choosable sets.
Cf. A072639, A140637, A326031, A355529, A367905, A368109, A370589, A370591, A370636, A370639, A370640.

Programs

  • Mathematica
    bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
fasmin[y_]:=Complement[y,Union@@Table[Union[s,#]& /@ Rest[Subsets[Complement[Union@@y,s]]],{s,y}]];
Table[Length[fasmin[Select[Subsets[Range[2,n]], Select[Tuples[bpe/@#],UnsameQ@@#&]=={}&]]],{n,0,10}]

A072640 Maximum position in A072660 where the value n occurs.

Original entry on oeis.org

0, 1, 3, 11, 100, 2090, 415729, 15670134831, 2990945138477441778, 28553369883190773267638351857949, 22025764139998888788032314837232820672093881927968648914
Offset: 0

Views

Author

Antti Karttunen, Jun 02 2002

Keywords

Crossrefs

Binary width of each term: A072642. Cf. A072638, A072639, A072654.

A072654 Maximum position in A072645 where the value n occurs.

Original entry on oeis.org

0, 1, 4, 17, 161, 11107, 39099276, 308061560269405, 11825896447872143037989337832, 10770594215935749279482183269315609406974195761679603097, 5521577958796399352092495436683350598124375604156506049598913887505725118345928241211637687725414588844260433
Offset: 0

Views

Author

Antti Karttunen, Jun 02 2002

Keywords

Crossrefs

Binary width of each term: A072655. Cf. A072638, A072639, A072640.

Extensions

a(10) from Sean A. Irvine, Oct 18 2024

A329554 Smallest MM-number of a set of n nonempty sets with no singletons.

Original entry on oeis.org

1, 13, 377, 16211, 761917, 55619941, 4393975339, 443791509239, 50148440544007, 6870336354528959, 954976753279525301, 142291536238649269849, 23193520406899830985387, 3873317907952271774559629, 701070541339361191195292849, 139513037726532877047863276951
Offset: 0

Views

Author

Gus Wiseman, Nov 17 2019

Keywords

Comments

A multiset multisystem is a finite multiset of finite multisets. A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. The multiset multisystem with MM-number n is formed by taking the multiset of prime indices of each part of the multiset of prime indices of n. For example, the prime indices of 78 are {1,2,6}, so the multiset multisystem with MM-number 78 is {{},{1},{1,2}}.

Examples

			The sequence of terms together with their corresponding systems begins:
       1: {}
      13: {{1,2}}
     377: {{1,2},{1,3}}
   16211: {{1,2},{1,3},{1,4}}
  761917: {{1,2},{1,3},{1,4},{2,3}}

Crossrefs

The smallest BII-number of a set of n sets is A000225(n).
BII-numbers of set-systems with no singletons are A326781.
MM-numbers of sets of nonempty sets are the odd terms of A302494.
MM-numbers of multisets of nonempty non-singleton sets are A320629.
The version with empty edges is A329556.
The version with singletons is A329557.
The version with empty edges and singletons is A329558.
Cf. A056239, A072639, A112798, A279952, A302242, A326031, A329552, A329556.
Classes of MM-numbers: A305078 (connected), A316476 (antichains), A318991 (chains), A320456 (covers), A329559 (clutters).

Programs

  • Mathematica
    sqvs=Select[Range[2,30],SquareFreeQ[#]&&!PrimeQ[#]&];
Table[Times@@Prime/@Take[sqvs,k],{k,0,Length[sqvs]}]

Formula

a(n) = Product_{i = 1..n} prime(A120944(i)).

A370643 Number of subsets of {2..n} such that it is not possible to choose a different binary index of each element.

Original entry on oeis.org

0, 0, 0, 0, 0, 1, 7, 23, 46, 113, 287, 680, 1546, 3374, 7191, 15008, 30016, 61013, 124354, 252577, 511229, 1031064, 2074281, 4164716, 8350912, 16729473, 33494928, 67034995, 134127390, 268325204, 536737665, 1073581062, 2147162124, 4294458549, 8589210382, 17178890873
Offset: 0

Views

Author

Gus Wiseman, Mar 10 2024

Keywords

Comments

A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793.

Examples

			The a(0) = 0 through a(7) = 23 subsets:
  .  .  .  .  .  {2,3,4,5}  {2,4,6}      {2,4,6}
                            {2,3,4,5}    {2,3,4,5}
                            {2,3,4,6}    {2,3,4,6}
                            {2,3,5,6}    {2,3,4,7}
                            {2,4,5,6}    {2,3,5,6}
                            {3,4,5,6}    {2,3,5,7}
                            {2,3,4,5,6}  {2,3,6,7}
                                         {2,4,5,6}
                                         {2,4,5,7}
                                         {2,4,6,7}
                                         {2,5,6,7}
                                         {3,4,5,6}
                                         {3,4,5,7}
                                         {3,4,6,7}
                                         {3,5,6,7}
                                         {4,5,6,7}
                                         {2,3,4,5,6}
                                         {2,3,4,5,7}
                                         {2,3,4,6,7}
                                         {2,3,5,6,7}
                                         {2,4,5,6,7}
                                         {3,4,5,6,7}
                                         {2,3,4,5,6,7}

Crossrefs

The case with ones allowed is A370637, differences A370589.
The minimal case is A370644, with ones A370642.
A048793 lists binary indices, A000120 length, A272020 reverse, A029931 sum.
A058891 counts set-systems, A003465 covering, A323818 connected.
A070939 gives length of binary expansion.
A096111 gives product of binary indices.
Cf. A072639, A326031, A355740, A367905, A368109.
Cf. A133686, A140637, A355529, A367867, A370583, A370636, A370640.

Programs

  • Mathematica
    bpe[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
Table[Length[Select[Subsets[Range[2,n]], Select[Tuples[bpe/@#],UnsameQ@@#&]=={}&]],{n,0,10}]

Extensions

More terms from Jinyuan Wang, Mar 28 2025
Previous Showing 31-40 of 50 results. Next

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