A371791 Number of biquanimous subsets of {1..n}. Sets with a subset having the same sum as the complement.

1, 1, 1, 2, 4, 8, 18, 38, 82, 175, 373, 787, 1651, 3439, 7126, 14667

Offset

0,4

Comments

A finite multiset of numbers is defined to be biquanimous iff it can be partitioned into two multisets with equal sums. Biquanimous partitions are counted by A002219 and ranked by A357976.

Links

Table of n, a(n) for n=0..15.

Example

For S = {1,3,4,6} we have {{1,6},{3,4}}, so S is counted under a(6).
The a(0) = 1 through a(6) = 18 subsets:
  {}  {}  {}  {}       {}         {}         {}
              {1,2,3}  {1,2,3}    {1,2,3}    {1,2,3}
                       {1,3,4}    {1,3,4}    {1,3,4}
                       {1,2,3,4}  {1,4,5}    {1,4,5}
                                  {2,3,5}    {1,5,6}
                                  {1,2,3,4}  {2,3,5}
                                  {1,2,4,5}  {2,4,6}
                                  {2,3,4,5}  {1,2,3,4}
                                             {1,2,3,6}
                                             {1,2,4,5}
                                             {1,2,5,6}
                                             {1,3,4,6}
                                             {2,3,4,5}
                                             {2,3,5,6}
                                             {3,4,5,6}
                                             {1,2,3,4,6}
                                             {1,2,4,5,6}
                                             {2,3,4,5,6}

Mathematica

biqQ[y_]:=MemberQ[Total/@Subsets[y], Total[y]/2];
Table[Length[Select[Subsets[Range[n]], biqQ]], {n, 0, 15}]

Crossrefs

First differences are A232466.

The complement is counted by A371792, differences A371793.

This is the "bi-" case of A371796, differences A371797.

A002219 aerated counts biquanimous partitions, ranks A357976.

A006827 and A371795 count non-biquanimous partitions, ranks A371731.

A108917 counts knapsack partitions, ranks A299702, strict A275972.

A237258 aerated counts biquanimous strict partitions, ranks A357854.

A321142 and A371794 count non-biquanimous strict partitions.

A321451 counts non-quanimous partitions, ranks A321453.

A321452 counts quanimous partitions, ranks A321454.

A366754 counts non-knapsack partitions, ranks A299729, strict A316402.

A371737 counts quanimous strict partitions, complement A371736.

A371781 lists numbers with biquanimous prime signature, complement A371782.

A371783 counts k-quanimous partitions.

Cf. A035470, A064914, A357879, A365661, A366320, A365381, A365925, A367094, A371788, A371789.

Sequence in context: A339158 A220839 A288206 * A218078 A110110 A300221

Adjacent sequences: A371788 A371789 A371790 * A371792 A371793 A371794

Keyword

nonn,more

Author

Gus Wiseman, Apr 07 2024

Status

approved