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 1-6 of 6 results.

A287764 Number of main classes of diagonal Latin squares of order n.

Original entry on oeis.org

1, 0, 0, 1, 2, 2, 972, 4873096, 3292326155394
Offset: 1

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Author

Eduard I. Vatutin, May 31 2017

Keywords

Crossrefs

Extensions

a(9) from Eduard I. Vatutin, Jul 06 2019

A274171 Number of diagonal Latin squares of order n with the first row in order.

Original entry on oeis.org

1, 0, 0, 2, 8, 128, 171200, 7447587840, 5056994653507584
Offset: 1

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Author

Eduard I. Vatutin, Jul 07 2016

Keywords

Comments

A diagonal Latin square is a Latin square in which both the main diagonal and main antidiagonal contain each element. - Andrew Howroyd, Sep 29 2020

Examples

			The a(4) = 2 diagonal Latin squares are:
   0 1 2 3   0 1 2 3
   2 3 0 1   3 2 1 0
   3 2 1 0   1 0 3 2
   1 0 3 2   2 3 0 1
.
The a(5) = 8 diagonal Latin squares are:
   0 1 2 3 4   0 1 2 3 4   0 1 2 3 4   0 1 2 3 4
   1 3 4 2 0   1 4 3 0 2   2 3 4 0 1   2 4 1 0 3
   4 2 1 0 3   3 2 1 4 0   4 0 1 2 3   4 0 3 2 1
   2 0 3 4 1   4 3 0 2 1   1 2 3 4 0   3 2 4 1 0
   3 4 0 1 2   2 0 4 1 3   3 4 0 1 2   1 3 0 4 2
.
   0 1 2 3 4   0 1 2 3 4   0 1 2 3 4   0 1 2 3 4
   3 4 0 1 2   3 4 1 2 0   4 2 0 1 3   4 2 3 0 1
   1 2 3 4 0   4 2 3 0 1   1 4 3 2 0   3 4 1 2 0
   4 0 1 2 3   2 0 4 1 3   3 0 1 4 2   1 3 0 4 2
   2 3 4 0 1   1 3 0 4 2   2 3 4 0 1   2 0 4 1 3
		

Crossrefs

Formula

a(n) = A274806(n)/n!.

Extensions

a(9) added from Vatutin et al. (2016) by Max Alekseyev, Oct 05 2016
a(9) corrected by Eduard I. Vatutin, Oct 20 2016

A274806 Number of diagonal Latin squares of order n.

Original entry on oeis.org

1, 0, 0, 48, 960, 92160, 862848000, 300286741708800, 1835082219864832081920
Offset: 1

Views

Author

Eduard I. Vatutin, Jul 07 2016

Keywords

Comments

A diagonal Latin square is a Latin square in which both the main diagonal and main antidiagonal contain each element. - Andrew Howroyd, Oct 05 2020

Crossrefs

Formula

a(n) = A274171(n) * n!.

Extensions

a(9) from Vatutin et al. (2016) added by Max Alekseyev, Oct 05 2016
a(9) corrected by Eduard I. Vatutin, Oct 20 2016

A337302 Number of X-based filling of diagonals in a diagonal Latin square of order n with the main diagonal in ascending order.

Original entry on oeis.org

1, 1, 0, 0, 4, 4, 80, 80, 4752, 4752, 440192, 440192, 59245120, 59245120, 10930514688, 10930514688, 2649865335040, 2649865335040, 817154768973824, 817154768973824, 312426715251262464, 312426715251262464, 145060238642780180480, 145060238642780180480
Offset: 0

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Author

Eduard I. Vatutin, Aug 22 2020

Keywords

Comments

Used for getting strong canonical forms (SCFs) of the diagonal Latin squares and for fast enumerating of the diagonal Latin squares based on equivalence classes.
For all t > 0, a(2*t) = a(2*t+1).

Examples

			For n=4 there are 4 different X-based fillings of diagonals with main diagonal fixed to [0 1 2 3]:
   0 . . 1   0 . . 1   0 . . 2   0 . . 2
   . 1 0 .   . 1 3 .   . 1 0 .   . 1 3 .
   . 3 2 .   . 0 2 .   . 3 2 .   . 0 2 .
   2 . . 3   2 . . 3   1 . . 3   1 . . 3
		

Crossrefs

Formula

a(n) = A337303(n)/n!.
a(n) = A000316(floor(n/2)). - Andrew Howroyd and Eduard I. Vatutin, Oct 08 2020

Extensions

More terms from Alois P. Heinz, Oct 08 2020
a(0)=1 prepended by Andrew Howroyd, Oct 09 2020

A337303 Number of X-based filling of diagonals in a diagonal Latin square of order n.

Original entry on oeis.org

1, 1, 0, 0, 96, 480, 57600, 403200, 191600640, 1724405760, 1597368729600, 17571056025600, 28378507272192000, 368920594538496000, 952903592436341145600, 14293553886545117184000, 55442575636536644075520000, 942523785821122949283840000, 5231730206388249282710863872000
Offset: 0

Views

Author

Eduard I. Vatutin, Aug 22 2020

Keywords

Comments

Used for getting strong canonical forms (SCFs) of the diagonal Latin squares and for fast enumerating of the diagonal Latin squares based on equivalence classes.

Examples

			One of the 96 X-based fillings of diagonals of a diagonal Latin square for order n=4:
1 . . 0
. 0 1 .
. 3 2 .
2 . . 3
		

Crossrefs

Programs

  • PARI
    \\ here b(n) is A000459.
    b(n) = {sum(m=0, n, sum(k=0, n-m, (-1)^k * binomial(n, k) * binomial(n-k, m) * 2^(2*k+m-n) * (2*n-2*m-k)! )); }
    a(n) = {2^(n\2) * b(n\2) * n!} \\ Andrew Howroyd, Mar 26 2023

Formula

a(n) = A337302(n)*n!.
a(n) = n!*A000316(floor(n/2)). - Andrew Howroyd, Mar 26 2023

Extensions

a(0)=1 prepended and terms a(16) and beyond from Andrew Howroyd, Mar 26 2023

A338084 Number of equivalence classes of X-based filling of diagonals in a diagonal Latin square of order 2n (or 2n+1).

Original entry on oeis.org

1, 0, 2, 3, 20, 67, 596
Offset: 0

Views

Author

Eduard I. Vatutin, Oct 08 2020

Keywords

Comments

Supplemental for A309283.
The number of solutions in an equivalence class with the main diagonal in ascending order is at most 4*2^n*n!. This maximum is only achieved for n >= 5. - Andrew Howroyd, Mar 27 2023

Examples

			From _Andrew Howroyd_, Mar 27 2023: (Start)
For n = 5, the following is an example solution in an equivalence class of maximum size. The second square shows the effect of swapping the two diagonals and renumbering so that the main diagonal is still in ascending order.
   0 . . . . . . . . 1    0 . . . . . . . . 1
   . 1 . . . . . . 0 .    . 1 . . . . . . 0 .
   . . 2 . . . . 3 . .    . . 2 . . . . 3 . .
   . . . 3 . . 2 . . .    . . . 3 . . 2 . . .
   . . . . 4 6 . . . .    . . . . 4 9 . . . .
   . . . . 7 5 . . . .    . . . . 6 5 . . . .
   . . . 5 . . 6 . . .    . . . 4 . . 6 . . .
   . . 8 . . . . 7 . .    . . 5 . . . . 7 . .
   . 9 . . . . . . 8 .    . 7 . . . . . . 8 .
   4 . . . . . . . . 9    8 . . . . . . . . 9
(End)
		

Crossrefs

Formula

a(n) >= A000316(n) / (4*2^n*n!). - Andrew Howroyd, Mar 27 2023
Showing 1-6 of 6 results.