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 1-9 of 9 results.

A307163 Minimum number of intercalates in a diagonal Latin square of order n.

Original entry on oeis.org

0, 0, 0, 12, 0, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Eduard I. Vatutin, Mar 27 2019

Keywords

Comments

An intercalate is a 2 X 2 subsquare of a Latin square.
Every diagonal Latin square is a Latin square, so 0 <= a(n) <= A307164(n) <= A092237(n). - Eduard I. Vatutin, Sep 21 2020
Every intercalate is a partial loop and every partial loop is a loop, so 0 <= a(n) <= A307170(n) <= A307166(n). - Eduard I. Vatutin, Oct 19 2020
a(n)=0 for all orders n for which cyclic diagonal Latin squares exist (see A007310) due to all cyclic diagonal Latin squares don't have intercalates. - Eduard I. Vatutin, Aug 07 2023
a(n)=0 for all orders n for which diagonalized cyclic diagonal Latin squares exist (see A372922) due to all diagonalized cyclic diagonal Latin squares don't have intercalates. - Eduard I. Vatutin, Sep 24 2024
a(16) <= 2, a(17) = 0, a(18) <= 9, a(19) = 0, a(20) <= 1, a(21) <= 11, a(22) <= 9, a(23) = 0, a(24) <= 16, a(25) = 0, a(26) <= 29. - Eduard I. Vatutin, added Sep 10 2023, updated Mar 01 2025

Crossrefs

Extensions

a(9) added by Eduard I. Vatutin, Sep 21 2020
a(10)-a(13) added by Eduard I. Vatutin, Apr 01 2021
a(14)-a(15) added by Eduard I. Vatutin, Sep 24 2024

A307164 Maximum number of intercalates in a diagonal Latin square of order n.

Original entry on oeis.org

0, 0, 0, 12, 4, 9, 30, 112, 72
Offset: 1

Views

Author

Eduard I. Vatutin, Mar 27 2019

Keywords

Comments

An intercalate is a 2 X 2 subsquare of a Latin square.
0 <= A307163(n) <= A307164(n) <= A092237(n). - Eduard I. Vatutin, Sep 21 2020
a(10) >= 109, a(11) >= 172, a(12) >= 324, a(13) >= 180, a(14) >= 391, a(15) >= 630, a(16) >= 960, a(17) >= 736, a(18) >= 547, a(19) >= 457, a(20) >= 1100, a(21) >= 785, a(22) >= 887, a(23) >= 899, a(24) >= 1680, a(25) >= 1700, a(26) >= 1299, a(27) >= 1372, a(28) >= 2892. - Eduard I. Vatutin, May 31 2021, updated Mar 02 2025
If, in theory, all unordered pairs of rows and columns form intercalate in their intersection, total number of intercalates will be (n*(n-1))^2, so a(n) <= (n*(n-1))^2, a(n) is asymptotically less than O(n^4). In practice a(n) << (n*(n-1))^2. - Eduard I. Vatutin, Mar 05 2025

Examples

			From _Eduard I. Vatutin_, May 31 2021: (Start)
One of the best known diagonal Latin squares of order n=5
  0 1 2 3 4
  4 2 0 1 3
  1 4 3 2 0
  3 0 1 4 2
  2 3 4 0 1
has 4 intercalates:
  . . 2 3 .   . . . . .   . . . . .   . . . . .
  . . . . .   . . 0 . 3   . . . . .   . . . . .
  . . 3 2 .   . . 3 . 0   1 . 3 . .   . 4 3 . .
  . . . . .   . . . . .   3 . 1 . .   . . . . .
  . . . . .   . . . . .   . . . . .   . 3 4 . .
so a(5)=4. (End)
		

Crossrefs

Extensions

a(9) added by Eduard I. Vatutin, Sep 21 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

A345370 a(n) is the number of distinct numbers of diagonal transversals that a diagonal Latin square of order n can have.

Original entry on oeis.org

1, 0, 0, 1, 2, 2, 14, 47, 182
Offset: 1

Views

Author

Eduard I. Vatutin, Jun 16 2021

Keywords

Comments

a(n) <= A287648(n) - A287647(n) + 1.
a(n) <= A287764(n).
Conjecture: a(12) = A287648(12) - A287647(12) + 1. - Natalia Makarova, Oct 26 2021
a(10) >= 736, a(11) >= 1344, a(12) >= 17693, a(13) >= 18241, a(14) >= 294053, a(15) >= 1958394, a(16) >= 13715. - Eduard I. Vatutin, Oct 29 2021, updated Mar 02 2025

Examples

			For n=7 the number of diagonal transversals that a diagonal Latin square of order 7 may have is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, or 27. Since there are 14 distinct values, a(7)=14.
		

Crossrefs

Extensions

a(8) added by Eduard I. Vatutin, Jul 15 2021
a(9) added by Eduard I. Vatutin, Oct 20 2022

A345761 a(n) is the number of distinct numbers of orthogonal diagonal mates that a diagonal Latin squares of order n can have.

Original entry on oeis.org

1, 0, 0, 1, 2, 1, 3, 31, 99
Offset: 1

Views

Author

Eduard I. Vatutin, Jun 26 2021

Keywords

Comments

a(n) <= A287695(n) + 1.
a(n) <= A287764(n).
a(10) >= 10. It seems that a(10) = 10 due to long computational experiments within the Gerasim@Home volunteer distributed computing project did not reveal the existence of diagonal Latin squares of order 10 with the number of orthogonal diagonal Latin squares different from {0, 1, 2, 3, 4, 5, 6, 7, 8, 10}.
a(11) >= 112, a(12) >= 5079. - Eduard I. Vatutin, Nov 02 2021, updated Jan 23 2023

Examples

			For n=7 the number of orthogonal diagonal Latin squares that a diagonal Latin square of order 7 may have is 0, 1, or 3. Since there are 3 distinct values, a(7)=3.
		

Crossrefs

A354050 a(n) is the number of distinct numbers of intercalates that an orthogonal diagonal Latin square of order n can have.

Original entry on oeis.org

0, 0, 0, 1, 1, 0, 3, 26, 55
Offset: 1

Views

Author

Eduard I. Vatutin, May 16 2022

Keywords

Comments

An orthogonal diagonal Latin square is a diagonal Latin square with at least one orthogonal diagonal mate. Since all orthogonal diagonal Latin squares are diagonal Latin squares, a(n) <= A345760(n).
a(10) >= 74, a(11) >= 76, a(12) >= 190. - updated by Eduard I. Vatutin, Mar 01 2025

Examples

			For n=8 the number of intercalates that an orthogonal diagonal Latin square of order 8 may have is 2, 4, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 36, 40, 44, 48, 52, 56, 64, 80, or 112. Since there are 26 distinct values, a(8)=26.
		

Crossrefs

A368182 a(n) is the number of distinct numbers of intercalates in Latin squares of order n.

Original entry on oeis.org

1, 1, 1, 2, 2, 9, 23, 61
Offset: 1

Views

Author

Eduard I. Vatutin, Feb 15 2024

Keywords

Comments

a(9)>=64, a(10)>=103, a(11)>=145, a(12)>=259, a(13)>=200, a(14)>=362, a(15)>=536, a(16)>=794, a(17)>=705, a(18)>=655, a(19)>=469, a(20)>=1362, a(21)>=985, a(22)>=1435, a(23)>=967, a(24)>=1754, a(25)>=1679, a(26)>=2040, a(28)>=2803. - Eduard I. Vatutin, added Aug 13 2024, updated Jun 25 2025

Examples

			For n=7, a Latin square of order 7 may have 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 18, 20, 22, 26, 30, or 42 intercalates. There are 23 possibilities, so a(7)=23.
		

Crossrefs

A382270 Maximum number of intercalates in a Brown's diagonal Latin square of order 2n.

Original entry on oeis.org

0, 12, 9, 112, 57
Offset: 1

Views

Author

Eduard I. Vatutin, Mar 20 2025

Keywords

Comments

A Brown's diagonal Latin square is a horizontally symmetric row-inverse or vertically symmetric column-inverse diagonal Latin square (see A339641).
Brown's diagonal Latin squares are special case of plain symmetry diagonal Latin squares that do not exist for odd orders.
a(6)>=252, a(7)>=385, a(8)>=960, a(9)>=329, a(10)>=356, a(11)>=497, a(12)>=1008, a(13)>=497, a(14)>=524.

Crossrefs

A382957 a(n) is the number of distinct numbers of intercalates in an extended self-orthogonal diagonal Latin squares of order n.

Original entry on oeis.org

1, 0, 0, 1, 1, 0, 3, 8, 52, 45
Offset: 1

Views

Author

Eduard I. Vatutin, Apr 10 2025

Keywords

Comments

A self-orthogonal diagonal Latin square (SODLS, see A329685) is a diagonal Latin square orthogonal to its transpose. An extended self-orthogonal diagonal Latin square (ESODLS, see A309210) is a diagonal Latin square that has an orthogonal diagonal Latin square from the same main class. SODLS is a special case of ESODLS.

Examples

			For n=7 the number of intercalates that an extended self-orthogonal diagonal Latin square of order 7 may have is 0, 10, or 18. Since there are 3 distinct values, a(7)=3.
		

Crossrefs

Showing 1-9 of 9 results.