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.

A287648 Maximum number of diagonal transversals in a diagonal Latin square of order n.

Original entry on oeis.org

1, 0, 0, 4, 5, 6, 27, 120, 333
Offset: 1

Views

Author

Eduard I. Vatutin, May 29 2017

Keywords

Comments

From Eduard I. Vatutin, Oct 04 2020: (Start)
A diagonal Latin square is a Latin square in which both the main diagonal and main antidiagonal contain each element.
A diagonal transversal is a transversal that includes exactly one element from the main diagonal and exactly one from the antidiagonal. For squares of odd orders, these elements can coincide at the intersection of the diagonals. (End)
A007016 is an upper bound for the number of diagonal transversals in a Latin square: A287647(n) <= a(n) <= A007016(n). - Eduard I. Vatutin, Jan 02 2020
a(11) >= 4828, a(12) >= 24901, a(13) >= 131106, a(14) >= 364596, a(15) >= 389318. - Natalia Makarova, Tomáš Brada, Harry White, Oct 04 2020
a(16) >= 32172800, a(18) >= 280308432. - Natalia Makarova, Tomáš Brada, Dec 25 2020
a(12) >= 28496. - Natalia Makarova, Harry White, Jan 23 2021
a(14) >= 380718, a(20) >= 90010806304, a(21) >= 51162162017, a(22) >= 3227747329246. The number of D-transversals for orders 20 - 22 was calculated by a volunteer. - Natalia Makarova, Tomáš Brada, Harry White, Mar 17 2021
All cyclic diagonal Latin squares (see A338562) are diagonal Latin squares, so A342997((n-1)/2) <= a(n). - Eduard I. Vatutin, Apr 26 2021
a(14) >= 383578, a(15) >= 398974. - Natalia Makarova, Tomáš Brada, Jan 13 2022
a(10) >= 890, a(12) >= 30192, a(14) >= 490218, a(15) >= 4620434, a(17) >= 204995269, a(18) >= 281593874, a(19) >= 11254190082. - Eduard I. Vatutin, Jul 22 2020, updated Mar 01 2025
For most orders n, at least one diagonal Latin square with the maximal number of diagonal transversals has an orthogonal mate and a(n) = A360220(n). Known exceptions: n=6 and n=10. - Eduard I. Vatutin, Feb 17 2023

Examples

			For example, the diagonal Latin square
  0 1 2 3
  3 2 1 0
  1 0 3 2
  2 3 0 1
has 4 diagonal transversals:
  0 . . .    . 1 . .    . . 2 .    . . . 3
  . . 1 .    . . . 0    3 . . .    . 2 . .
  . . . 2    . . 3 .    . 0 . .    1 . . .
  . 3 . .    2 . . .    . . . 1    . . 0 .
In addition there are 4 other transversals that are not diagonal transversals and are therefore not included here.
From _Natalia Makarova_, Oct 04 2020: (Start)
The following DLS of order 14 has 364596 diagonal transversals:
   0  7  6 11  9  3  4  5  2 12 13  8 10  1
   6  1 11  5 10 12  2  3  9  7  4 13  0  8
   5 11  2 12  8  1  7 10  0  6  9  3 13  4
  13  6  5  3  1 10  9 12  7  0  2  4  8 11
  12  3 10  1  4 13  8  6 11  5  0  7  2  9
  10 12  1  8  2  5 11 13  4  3  6  0  9  7
   9  2  7  0  5 11  6  8 13  4  1 10  3 12
   4 13  3  9  6  0 10  7  1  8 12  2 11  5
   2  4  9 10 11  6  1  0  8 13  7 12  5  3
   1 10  8 13 12  2  5  4  3  9 11  6  7  0
   3  5 12  7 13  8  0  1  6 11 10  9  4  2
   8  0 13  4  7  9  3  2 12 10  5 11  1  6
   7  9  0  6  3  4 13 11  5  2  8  1 12 10
  11  8  4  2  0  7 12  9 10  1  3  5  6 13
(End)
		

References

  • J. W. Brown, F. Cherry, L. Most, M. Most, E. T. Parker, and W. D. Wallis, Completion of the spectrum of orthogonal diagonal Latin squares, Lecture notes in pure and applied mathematics. 1992. Vol. 139. pp. 43-49.

Crossrefs

Extensions

a(8) added by Eduard I. Vatutin, Oct 29 2017
a(9) added by Eduard I. Vatutin, Dec 08 2020

A287647 Minimum number of diagonal transversals in a diagonal Latin square of order n.

Original entry on oeis.org

1, 0, 0, 4, 1, 2, 0, 0, 0
Offset: 1

Views

Author

Eduard I. Vatutin, May 29 2017

Keywords

Comments

A007016 is an upper bound for the number of diagonal transversals in a Latin square: a(n) <= A287648(n) <= A007016(n). - Eduard I. Vatutin, Jan 02 2020
From Eduard I. Vatutin, Apr 26 2021: (Start)
A diagonal Latin square is a Latin square in which both the main diagonal and main antidiagonal contain each element.
A diagonal transversal is a transversal that includes exactly one element from the main diagonal and exactly one from the antidiagonal. For squares of odd orders, these elements can coincide at the intersection of the diagonals.
All cyclic diagonal Latin squares (see A338562) are diagonal Latin squares, so a(n) <= A342998((n-1)/2). (End)
a(10) <= 3, a(11) <= 43, a(12) = 0, a(13) <= 4756, a(14) <= 1446, a(15) <= 15510, a(16) <= 898988, a(17) <= 12058840, a(18) <= 82577875, a(19) <= 592174879, a(20) <= 4488686380. - Eduard I. Vatutin, Sep 26 2021, updated Jan 20 2025

Examples

			From _Eduard I. Vatutin_, Apr 26 2021: (Start)
For example, the diagonal Latin square
  0 1 2 3
  3 2 1 0
  1 0 3 2
  2 3 0 1
has 4 diagonal transversals:
  0 . . .    . 1 . .    . . 2 .    . . . 3
  . . 1 .    . . . 0    3 . . .    . 2 . .
  . . . 2    . . 3 .    . 0 . .    1 . . .
  . 3 . .    2 . . .    . . . 1    . . 0 .
In addition there are 4 other transversals that are not diagonal transversals and are therefore not included here. (End)
		

Crossrefs

Extensions

a(8) added by Eduard I. Vatutin, Oct 29 2017
a(9) added by Eduard I. Vatutin, Sep 20 2020

A287644 Maximum number of transversals in a diagonal Latin square of order n.

Original entry on oeis.org

1, 0, 0, 8, 15, 32, 133, 384, 2241
Offset: 1

Views

Author

Eduard I. Vatutin, May 29 2017

Keywords

Comments

Same as the maximum number of transversals in a Latin square of order n except n = 3.
a(10) >= 5504 from Parker and Brown.
Every diagonal Latin square is a Latin square and every orthogonal diagonal Latin square is a diagonal Latin square, so 0 <= A287645(n) <= A357514(n) <= a(n) <= A090741(n). - Eduard I. Vatutin, added Sep 20 2020, updated Mar 03 2023
a(11) >= 37851, a(12) >= 198144, a(13) >= 1030367, a(14) >= 3477504, a(15) >= 36362925, a(16) >= 244744192, a(17) >= 1606008513, a(19) >= 87656896891, a(23) >= 452794797220965, a(25) >= 41609568918940625. - Eduard I. Vatutin, Mar 08 2020, updated Mar 10 2022
Also a(n) is the maximum number of transversals in an orthogonal diagonal Latin square of order n for all orders except n=6 where orthogonal diagonal Latin squares don't exist. - Eduard I. Vatutin, Jan 23 2022
All cyclic diagonal Latin squares are diagonal Latin squares, so A348212((n-1)/2) <= a(n) for all orders n of which cyclic diagonal Latin squares exist. - Eduard I. Vatutin, Mar 25 2021

References

  • J. W. Brown et al., Completion of the spectrum of orthogonal diagonal Latin squares, Lecture notes in pure and applied mathematics, volume 139 (1992), pp. 43-49.
  • E. T. Parker, Computer investigations of orthogonal Latin squares of order 10, Proc. Sympos. Appl. Math., volume 15 (1963), pp. 73-81.

Crossrefs

Extensions

a(8) added by Eduard I. Vatutin, Oct 29 2017
a(9) added by Eduard I. Vatutin, Sep 20 2020

A344105 a(n) is the number of distinct numbers of transversals of order n diagonal Latin squares.

Original entry on oeis.org

1, 0, 0, 1, 2, 1, 32, 73, 406
Offset: 1

Views

Author

Eduard I. Vatutin, Jun 22 2021

Keywords

Comments

a(n) <= A287644(n) - A287645(n) + 1.
a(n) <= A287764(n).
Diagonal Latin squares are a special case of Latin squares, so a(n) <= A309344(n).
a(10) >= 459, a(11) >= 6437, a(12) >= 23707, a(13) >= 75891, a(14) >= 290681. - Eduard I. Vatutin, Oct 29 2021, updated Mar 01 2025
For all spectra of even orders all known values included in them are divisible by 2. For all spectra of orders n=6, n=10 and n=14 (and probably for all n=4k+2) all known values included in the corresponding spectra are divisible by 4. This leads to the following hypothesis: a(2k) <= (A287644(2k) - A287645(2k) + 2)/2 and a(4k+2) <= (A287644(4k+2) - A287645(4k+2) + 4)/4, where w(n) = A287644(n) - A287645(n) + 1 is a width of corresponding spectra and (w(n)+1)/2 is done to round the result of the division up. - Eduard I. Vatutin, Mar 21 2022

Examples

			For n=7 the number of transversals that a diagonal Latin square of order 7 may have is 7, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 37, 41, 43, 45, 47, 55, or 133. Since there are 32 distinct values, a(7)=32.
		

Crossrefs

Extensions

a(8) added by Eduard I. Vatutin, Jul 14 2021
a(9) added by Eduard I. Vatutin, Nov 20 2022

A357514 Minimum number of transversals in an orthogonal diagonal Latin square of order n.

Original entry on oeis.org

1, 0, 0, 8, 15, 0, 23, 16, 132
Offset: 1

Views

Author

Eduard I. Vatutin, Oct 01 2022

Keywords

Comments

Orthogonal diagonal Latin squares is a diagonal Latin squares that have at least one orthogonal diagonal mate.
a(10) <= 652, a(11) <= 2091, a(12) <= 6240. - Eduard I. Vatutin, Oct 01 2022, updated Oct 21 2024
Every diagonal Latin square is a Latin square and every orthogonal diagonal Latin square is a diagonal Latin square, so 0 <= A287645(n) <= a(n) <= A287644(n) <= A090741(n). - Eduard I. Vatutin, Feb 17 2023

Crossrefs

A348212 Number of transversals in a cyclic diagonal Latin square of order 2n+1.

Original entry on oeis.org

1, 0, 15, 133, 0, 37851, 1030367, 0, 1606008513, 87656896891, 0, 452794797220965, 41609568918940625
Offset: 1

Views

Author

Eduard I. Vatutin, Oct 07 2021

Keywords

Comments

All cyclic diagonal Latin squares of order n have same number of transversals. A similar statement for diagonal transversals is not true (see A342998 and A342997).
All broken diagonals and antidiagonals of cyclic Latin squares are transversals, so a(n) >= 2*n for all n > 1 for which cyclic diagonal Latin squares exist. - Eduard I. Vatutin, Mar 22 2022
All cyclic diagonal Latin squares are diagonal Latin squares, so A287645(2n+1) <= a(n) <= A287644(2n+1) for all orders in which cyclic diagonal Latin squares exist. - Eduard I. Vatutin, Mar 23 2022

Examples

			A cyclic diagonal Latin square of order 5
  0 1 2 3 4
  2 3 4 0 1
  4 0 1 2 3
  1 2 3 4 0
  3 4 0 1 2
has a(3)=15 transversals:
  0 . . . .   0 . . . .   . 1 . . .         . . . . 4
  . 3 . . .   . . . . 1   2 . . . .         . 3 . . .
  . . 1 . .   . . . 2 .   . . . . 3         . . . 2 .
  . . . 4 .   . . 3 . .   . . . 4 .         1 . . . .
  . . . . 2   . 4 . . .   . . 0 . .   ...   . . 0 . .
		

Crossrefs

Formula

a(n) = A006717(n) * A011655(n+1).

A383684 Minimum number of transversals in an extended self-orthogonal diagonal Latin square of order n.

Original entry on oeis.org

1, 0, 0, 8, 15, 0, 23, 128, 133, 716
Offset: 1

Views

Author

Eduard I. Vatutin, May 05 2025

Keywords

Comments

A self-orthogonal diagonal Latin square (SODLS) is a diagonal Latin square orthogonal to its transpose. An extended self-orthogonal diagonal Latin square (ESODLS) is a diagonal Latin square that has an orthogonal diagonal Latin square from the same main class. SODLS is a special case of ESODLS.

Crossrefs

A387124 Maximum number of transversals in an extended self-orthogonal diagonal Latin square of order n.

Original entry on oeis.org

1, 0, 0, 8, 15, 0, 133, 384, 2241, 988
Offset: 1

Views

Author

Eduard I. Vatutin, Aug 17 2025

Keywords

Comments

A self-orthogonal diagonal Latin square (SODLS) is a diagonal Latin square orthogonal to its transpose. An extended self-orthogonal diagonal Latin square (ESODLS) is a diagonal Latin square that has an orthogonal diagonal Latin square from the same main class. SODLS is a special case of ESODLS.

Crossrefs

Showing 1-8 of 8 results.