A343697 -id:A343697 - cp's OEIS frontend

A343696 a(n) is the number of preference profiles in the stable marriage problem with n men and n women, such that the men's preference profiles form a Latin square.

1, 8, 2592, 191102976, 4013162496000000, 113241608573209804800000000, 5078594244241245901264634511360000000000, 759796697672599288560347581750936194390876487680000000000, 602809439070636186475532789128702956081602819845966698324215778508800000000000

Offset: 1

Tanya Khovanova and MIT PRIMES STEP Senior group, May 25 2021

nonn

Equivalently, these are the profiles where each woman is ranked differently by the n men.
Equivalently, for every rank i, there is exactly one woman who is ranked i by a given man.
The men-proposing Gale-Shapley algorithm on such a set of preferences ends in one round, since every woman receives one proposal in the first round.
Due to symmetry, a(n) is the number of preference profiles in the stable marriage problem with n men and n women, such that the women’s preference profiles form a Latin square.

			For n = 3, there are 3!^3 ways to set up the women's preference profiles and A002860(3) ways to set up the men's preference profiles, where A002860(3) = 12 (there are 12 different Latin squares of order 3). Thus a(3) = 3!^3 * A002860(3) = 216 * 12 = 2592.

Matvey Borodin, Eric Chen, Aidan Duncan, Tanya Khovanova, Boyan Litchev, Jiahe Liu, Veronika Moroz, Matthew Qian, Rohith Raghavan, Garima Rastogi, and Michael Voigt, Sequences of the Stable Matching Problem, arXiv:2201.00645 [math.HO], 2021.
Wikipedia, Gale-Shapley algorithm.

Cf. A002860, A185141, A343697.

a(n) = n!^n * A002860(n).

A344662 a(n) is the number of preference profiles in the stable marriage problem with n men and n women so that they form n pairs of people of different genders who rank each other first, and so that the men's preferences arranged in a matrix form a Latin square.

Original entry on oeis.org

1, 2, 96, 746496, 1284211998720, 2427160677580800000000, 6166762687851449045483520000000000, 45287412266290145430585597857888710164480000000000, 1555956528335898586085189699733983238252540690603399394099200000000000, 395245501240598487865502317687285665641954608158944047815164739503046322343116800000000000000

Offset: 1

Tanya Khovanova and MIT PRIMES STEP Senior group, May 30 2021

nonn

Two people who rank each other first are called soulmates. The profiles in this sequence are required to have n pairs of soulmates.
The profiles with n pairs of soulmates are counted by sequence A343698. The profiles such that the men's preference form a Latin square are counted by A343696. The profiles in this sequence are the intersection of profiles in A343696 and A343698.
The Gale-Shapley algorithm (both men-proposing and women-proposing) on the preference profiles described by this sequence ends in one round.

			For n = 3, there are A002860(3) = 12 ways to set up the men's preference profiles, where A002860(n) is the number of Latin squares of order n. The men's first preferences set the women's first preferences, so we only need to complete the women's profiles with other preferences, which can be done in 2!^3 = 8 ways. Thus, A344662(3) = 12 * 8 = 96.

Matvey Borodin, Eric Chen, Aidan Duncan, Tanya Khovanova, Boyan Litchev, Jiahe Liu, Veronika Moroz, Matthew Qian, Rohith Raghavan, Garima Rastogi, and Michael Voigt, Sequences of the Stable Matching Problem, arXiv:2201.00645 [math.HO], 2021.
Wikipedia, Gale-Shapley algorithm.

Cf. A002860, A185141, A343694, A343695, A343696, A343697, A343698, A344663.

a(n) = (n-1)!^n * A002860(n) = A343696(n)/n^n.

A344664 a(n) is the number of preference profiles in the stable marriage problem with n men and n women where both the men's and the women's preferences form a Latin square when arranged in a matrix. In addition, it is possible to arrange all people into n man-woman couples such that they rank each other first.

Original entry on oeis.org

1, 2, 24, 13824, 216760320, 917676490752000, 749944260264355430400000, 293457967200879687743551498616832000, 84112872283641495670736269523436185936222748672000, 27460610008848610956892895086773773421767179663217968124264448000000

Offset: 1

Tanya Khovanova and MIT PRIMES STEP Senior group, Jun 01 2021

nonn

Two people who rank each other first are called soulmates. Thus, the profiles in this sequence have n pairs of soulmates.
The profiles with n pairs of soulmates are counted by sequence A343698. The profiles such that the men's preferences form a Latin square are counted by A343696. The profiles such that both men's and women's preferences form a Latin square are counted by A343697. The profiles in this sequence are the intersection of profiles in A343698 and A343697.
Both the men- and the women-proposing Gale-Shapley algorithm on the preference profiles described by this sequence end in one round.

			For n = 3, there are A002860(3) = 12 Latin squares of order 3. Thus, there are A002860(3) = 12 ways to set up the men's preference profiles. After that, the women's preference profiles form a Latin square with a fixed first column, as the first column is uniquely defined to generate 3 pairs of soulmates. Thus, there are A002860(3)/3! = 12/6 = 2 ways to set up the women's preference profiles, making a(3) = 12 * 2 = 24 preference profiles.

Matvey Borodin, Eric Chen, Aidan Duncan, Tanya Khovanova, Boyan Litchev, Jiahe Liu, Veronika Moroz, Matthew Qian, Rohith Raghavan, Garima Rastogi, and Michael Voigt, Sequences of the Stable Matching Problem, arXiv:2201.00645 [math.HO], 2021.
Wikipedia, Gale-Shapley algorithm.

Cf. A000479, A002860, A185141, A343696, A343697, A343698, A344665.

a(n) = A002860(n)^2 / n!.

a(n) = A000479(n) * A002860(n).

Corrected by Tanya Khovanova, Aug 17 2021

A344665 a(n) is the number of preference profiles in the stable marriage problem with n men and n women, where both the men's preferences and women's preferences form a Latin square when arranged in a matrix, with no paired man and woman who rank each other first.

Original entry on oeis.org

0, 2, 48, 124416, 9537454080, 243184270049280000, 1390396658530114967961600000, 4352862027490648408300099378983469056000, 11228731998377005106060609036300637077741992056717312000, 36658843398022550531624696117934603340895735930389121945136191766528000000

Offset: 1

Tanya Khovanova and MIT PRIMES STEP Senior group, Jun 22 2021

nonn

The profiles in this sequence are the intersection of the profiles in A343696 and A343697. The Gale-Shapley algorithm on such a set of preference profiles ends in one round.

			For n = 2, there are A002860(2) = 2 ways to set up the men's profiles. Since the women don't want to rank the man who ranked them first as first, there is exactly 1 way to set up the women's profiles. So, there are 2 * 1 = 2 preference profiles for n = 2.

Matvey Borodin, Eric Chen, Aidan Duncan, Tanya Khovanova, Boyan Litchev, Jiahe Liu, Veronika Moroz, Matthew Qian, Rohith Raghavan, Garima Rastogi, and Michael Voigt, Sequences of the Stable Matching Problem, arXiv:2201.00645 [math.HO], 2021.
Wikipedia, Gale-Shapley algorithm.

Cf. A002860, A185141, A343696, A343697, A344664.

a(n) = A002860(n)^2 * Sum_{i=0..n} (-1)^i/i! = A344664(n) * A000166(n).

A351413 a(n) is the maximum number of stable matchings in the Latin Stable Marriage Problem of order n.

Original entry on oeis.org

1, 2, 3, 10, 9, 48, 61

Offset: 1

Dan Eilers, Feb 10 2022

In the Latin Stable Marriage Problem of order n, the sum of a man and woman's rankings of each other is n+1. This implies that the men's and women's ranking tables are Latin squares. As a subproblem of the Stable Marriage Problem, Latin instances provide lower bounds for the maximum number of stable matchings in the general problem, such as A005154 and A065982. For sizes 1 to 4, Latin instances provide exact bounds; they are conjectured to provide exact bounds for sizes a power of 2; they provide the best lower bounds known for sizes 6, 10, 12, and 24, of 48, 1000, 6472, and 126112960, respectively.
The next term, a(8), is conjectured to be 268, consistent with A005154. The minimum number of stable matchings for Latin instances of order n is n, and is realized for the cyclic group of order n. The average number of stable matchings is 7 for n=4 (cf. A351430 showing an average of about 1.5 for the general problem), and benefits from avoidance of mutual first choices and more generally the lack of overlap between the men's and women's preferred matchings. The Latin squares of A005154 and A065982 can be interpreted as multiplication tables of groups, n-th powers of the cyclic group C2 and n-th dihedral groups, respectively.
The sequence decreases from a(4)=10 to a(5)=9, in contrast to the corresponding sequence for the general problem, which Thurber showed to be strictly increasing. This has motivated the study of less restrictive subproblems, such as pseudo-Latin squares (A069124, A069156), Latin x Latin instances (A344664, A344665, A343697), instances where participants have different first choices (A343475, A343694, A343695), or instances with unspecified/tied/template rankings (A284458 with only first choices specified).
The sequence is empirically derived, originally based on reduced Latin squares (A000315). There are fewer instances to try using RC-equivalent Latin squares (A123234) instead of reduced Latin squares.

			Maximal instance of order 2 with 2 stable matchings:
  12
  21
Maximal instance of order 3 with 3 stable matchings:
  123
  231
  312
Maximal instance of order 4 with 10 stable matchings (group C2xC2):
  1234
  2143
  3412
  4321
Maximal instance of order 5 with 9 stable matchings:
  12345
  21453
  34512
  45231
  53124
Maximal instance of order 6 with 48 stable matchings (Dihedral group):
  123456
  214365
  365214
  456123
  541632
  632541
Maximal instance of order 7 with 61 stable matchings:
  1234567
  2316745
  3125476
  4657312
  5743621
  6471253
  7562134

C. Converse, Lower bounds for the maximum number of stable pairings for the general marriage problem based on the latin marriage problem, Ph. D. Thesis, Claremont Graduate School, Claremont, CA (1992) [Examples are from 69-70].

A. T. Benjamin, C. Converse, and H. A. Krieger, Note. How do I marry thee? Let me count the ways, Discrete Appl. Math. 59 (1995) 285-292.
Matvey Borodin, Eric Chen, Aidan Duncan, Tanya Khovanova, Boyan Litchev, Jiahe Liu, Veronika Moroz, Matthew Qian, Rohith Raghavan, Garima Rastogi, and Michael Voigt, Sequences of the Stable Matching Problem, arXiv:2201.00645 [math.HO], 2021 [Sections 3.7 and 4.2].
J. S. Hwang, Complete stable marriages and systems of I-M preferences, In: McAvaney K.L. (eds) Combinatorial Mathematics VIII. Lecture Notes in Mathematics, vol 884. Springer, Berlin, Heidelberg (1981) 49-63.
E. G. Thurber, Concerning the maximum number of stable matchings in the stable marriage problem, Discrete Math., 248 (2002), 195-219.

Cf. A005154 (powers of 2), A065982 (multiples of 2), A069156 (not necessarily Latin), A000315 (reduced Latin squares), A123234 (RC-equivalent Latin squares).

cp's OEIS Frontend

A343696 a(n) is the number of preference profiles in the stable marriage problem with n men and n women, such that the men's preference profiles form a Latin square.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Formula

A344662 a(n) is the number of preference profiles in the stable marriage problem with n men and n women so that they form n pairs of people of different genders who rank each other first, and so that the men's preferences arranged in a matrix form a Latin square.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Formula

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Formula

Extensions

A344665 a(n) is the number of preference profiles in the stable marriage problem with n men and n women, where both the men's preferences and women's preferences form a Latin square when arranged in a matrix, with no paired man and woman who rank each other first.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Formula

A351413 a(n) is the maximum number of stable matchings in the Latin Stable Marriage Problem of order n.

Views

Author

Keywords

Comments

Examples

References

Links

Crossrefs