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.

Previous Showing 11-18 of 18 results.

A375475 Number of main classes of diagonalized cyclic diagonal Latin squares of order 2n+1.

Original entry on oeis.org

1, 0, 1, 1, 7, 81, 2933
Offset: 0

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Author

Eduard I. Vatutin, Aug 17 2024

Keywords

Comments

Diagonalized cyclic diagonal Latin squares are diagonal Latin squares that are isomorphic to cyclic Latin squares. They are can be obtained from cyclic Latin squares (see A338522) by diagonalization (getting a corresponding pair of transversals and placing them on the diagonals, see article). Diagonalized cyclic diagonal Latin squares have some interesting properties, for example, there are a large number of diagonal transversals for diagonal Latin squares of odd orders.

Crossrefs

A343866 Number of inequivalent cyclic diagonal Latin squares of order 2n+1 up to rotations, reflections and permutation of symbols.

Original entry on oeis.org

1, 0, 1, 1, 0, 2, 3, 0, 4, 4, 0, 5, 3, 0, 7, 7, 0, 2, 9, 0, 10, 10, 0, 11, 7, 0, 13, 4, 0, 14, 15, 0, 6, 16, 0, 17, 18, 0, 8, 19, 0, 20, 8, 0, 22, 10, 0, 8, 24, 0, 25, 25, 0, 26, 27, 0, 28, 10, 0, 14, 22, 0, 13, 31, 0, 32, 16, 0, 34, 34, 0, 20, 14, 0, 37, 37, 0, 14, 39, 0, 20
Offset: 0

Views

Author

Andrew Howroyd, May 02 2021

Keywords

Comments

Also the number of main classes of diagonal Latin squares of order 2n+1 that contain a cyclic Latin square. Compare A341585.

Examples

			a(12) = 3 since there are A123565(25) = 10 cyclic diagonal Latin squares whose first row is in ascending order. Each of these is uniquely defined by the step between rows and form 5 pairs by horizontal or vertical reflection (negating the step between rows). Up to exchanging rows with columns there are 3 distinct classes, so a(12) = 3.
		

Crossrefs

Programs

  • PARI
    iscanon(n,k,g) = k <= vecmin(g*k%n) && k <= vecmin(g*lift(1/Mod(k,n))%n)
    a(n)={if(n==0, 1, my(m=2*n+1); sum(k=1, m-1, gcd(m,k)==1 && gcd(m,k-1)==1 && gcd(m,k+1)==1 && iscanon(m, k, [1,-1])))}

Formula

a((p-1)/2) = A341585((p-1)/2) for odd prime p.

A366331 Number of main classes of diagonal Latin squares of order 2n+1 that contain a horizontally semicyclic Latin square.

Original entry on oeis.org

1, 0, 1, 1, 0, 2, 20, 0, 272, 1208, 0, 127334, 1958084, 0
Offset: 0

Views

Author

Eduard I. Vatutin, Oct 07 2023

Keywords

Comments

A horizontally semicyclic diagonal Latin square is a square where each row r(i) is a cyclic shift of the first row r(0) by some value d(i) (see example).

Examples

			Example of horizontally semicyclic diagonal Latin square of order 13:
   0  1  2  3  4  5  6  7  8  9 10 11 12
   2  3  4  5  6  7  8  9 10 11 12  0  1  (d=2)
   4  5  6  7  8  9 10 11 12  0  1  2  3  (d=4)
   9 10 11 12  0  1  2  3  4  5  6  7  8  (d=9)
   7  8  9 10 11 12  0  1  2  3  4  5  6  (d=7)
  12  0  1  2  3  4  5  6  7  8  9 10 11  (d=12)
   3  4  5  6  7  8  9 10 11 12  0  1  2  (d=3)
  11 12  0  1  2  3  4  5  6  7  8  9 10  (d=11)
   6  7  8  9 10 11 12  0  1  2  3  4  5  (d=6)
   1  2  3  4  5  6  7  8  9 10 11 12  0  (d=1)
   5  6  7  8  9 10 11 12  0  1  2  3  4  (d=5)
  10 11 12  0  1  2  3  4  5  6  7  8  9  (d=10)
   8  9 10 11 12  0  1  2  3  4  5  6  7  (d=8)
		

Crossrefs

Extensions

a(11)-a(13) from Andrew Howroyd, Nov 02 2023

A368027 Number of Dabbaghian-Wu pandiagonal Latin squares of order 2n+1.

Original entry on oeis.org

1, 0, 0, 24, 0, 0, 72, 0, 0, 108, 0, 0, 4, 0, 0, 180, 0, 3, 216, 0, 0, 252, 0, 0, 264, 0, 0, 0, 0, 0, 360, 0, 5, 396, 0, 0, 432, 0, 0, 468, 0, 0, 0, 0, 0, 868, 0, 5, 576, 0
Offset: 1

Views

Author

Eduard I. Vatutin, Dec 16 2023

Keywords

Comments

A pandiagonal Latin square is a Latin square in which the diagonal, antidiagonal and all broken diagonals and antidiagonals are transversals.
A Dabbaghian-Wu pandiagonal Latin square is a special type of pandiagonal Latin square (see A342306). Such squares are constructed from cyclic diagonal Latin squares (see A338562) for prime orders n=6k+1 (see Dabbaghian and Wu article) using a polynomial algorithm based on permutation of some values in Latin square. For other orders (25, 35, 49, ...) this algorithm also ensures correct pandiagonal Latin squares.

Examples

			n=13=6*2+1 (prime order):
.
  4 0 2 3 1 5 6 7 11 9 10 12 8
  11 12 1 10 6 2 4 5 3 7 8 9 0
  9 10 11 2 0 1 3 12 8 4 6 7 5
  6 8 9 7 11 12 0 4 2 3 5 1 10
  5 7 3 12 8 10 11 9 0 1 2 6 4
  3 4 8 6 7 9 5 1 10 12 0 11 2
  1 2 0 4 5 6 10 8 9 11 7 3 12
  0 9 5 1 3 4 2 6 7 8 12 10 11
  10 1 12 0 2 11 7 3 5 6 4 8 9
  8 6 10 11 12 3 1 2 4 0 9 5 7
  2 11 7 9 10 8 12 0 1 5 3 4 6
  7 5 6 8 4 0 9 11 12 10 1 2 3
  12 3 4 5 9 7 8 10 6 2 11 0 1
.
n=19=6*3+1 (prime order):
.
  8 0 2 3 4 6 17 7 1 9 10 11 12 13 14 15 16 5 18
  5 6 7 8 16 10 0 11 13 14 15 17 9 18 12 1 2 3 4
  10 4 12 13 14 15 16 17 18 0 8 2 11 3 5 6 7 9 1
  14 16 17 18 1 12 2 15 4 5 6 7 8 9 10 11 0 13 3
  1 2 3 11 5 14 6 8 9 10 12 4 13 7 15 16 17 18 0
  18 7 8 9 10 11 12 13 14 3 16 6 17 0 1 2 4 15 5
  11 12 13 15 7 16 10 18 0 1 2 3 4 5 6 14 8 17 9
  16 17 6 0 9 1 3 4 5 7 18 8 2 10 11 12 13 14 15
  2 3 4 5 6 7 8 9 17 11 1 12 14 15 16 18 10 0 13
  7 8 10 2 11 5 13 14 15 16 17 18 0 1 9 3 12 4 6
  12 1 14 4 15 17 18 0 2 13 3 16 5 6 7 8 9 10 11
  17 18 0 1 2 3 4 12 6 15 7 9 10 11 13 5 14 8 16
  3 5 16 6 0 8 9 10 11 12 13 14 15 4 17 7 18 1 2
  15 9 18 10 12 13 14 16 8 17 11 0 1 2 3 4 5 6 7
  13 14 15 16 17 18 7 1 10 2 4 5 6 8 0 9 3 11 12
  0 11 1 14 3 4 5 6 7 8 9 10 18 12 2 13 15 16 17
  4 13 5 7 8 9 11 3 12 6 14 15 16 17 18 0 1 2 10
  9 10 11 12 13 2 15 5 16 18 0 1 3 14 4 17 6 7 8
  6 15 9 17 18 0 1 2 3 4 5 13 7 16 8 10 11 12 14
.
n=25=6*4+1 (nonprime order):
.
  5 1 2 3 4 15 6 7 8 9 0 11 12 13 14 20 16 17 18 19 10 21 22 23 24
  3 4 20 6 7 8 9 15 11 12 13 14 5 16 17 18 19 0 21 22 23 24 10 1 2
  6 7 8 9 0 11 12 13 14 20 16 17 18 19 5 21 22 23 24 15 1 2 3 4 10
  9 15 11 12 13 14 0 16 17 18 19 10 21 22 23 24 5 1 2 3 4 20 6 7 8
  12 13 14 5 16 17 18 19 0 21 22 23 24 15 1 2 3 4 10 6 7 8 9 20 11
  20 16 17 18 19 10 21 22 23 24 5 1 2 3 4 15 6 7 8 9 0 11 12 13 14
  18 19 0 21 22 23 24 10 1 2 3 4 20 6 7 8 9 15 11 12 13 14 5 16 17
  21 22 23 24 15 1 2 3 4 10 6 7 8 9 0 11 12 13 14 20 16 17 18 19 5
  24 5 1 2 3 4 20 6 7 8 9 15 11 12 13 14 0 16 17 18 19 10 21 22 23
  2 3 4 10 6 7 8 9 20 11 12 13 14 5 16 17 18 19 0 21 22 23 24 15 1
  15 6 7 8 9 0 11 12 13 14 20 16 17 18 19 10 21 22 23 24 5 1 2 3 4
  8 9 15 11 12 13 14 5 16 17 18 19 0 21 22 23 24 10 1 2 3 4 20 6 7
  11 12 13 14 20 16 17 18 19 5 21 22 23 24 15 1 2 3 4 10 6 7 8 9 0
  14 0 16 17 18 19 10 21 22 23 24 5 1 2 3 4 20 6 7 8 9 15 11 12 13
  17 18 19 0 21 22 23 24 15 1 2 3 4 10 6 7 8 9 20 11 12 13 14 5 16
  10 21 22 23 24 5 1 2 3 4 15 6 7 8 9 0 11 12 13 14 20 16 17 18 19
  23 24 10 1 2 3 4 20 6 7 8 9 15 11 12 13 14 5 16 17 18 19 0 21 22
  1 2 3 4 10 6 7 8 9 0 11 12 13 14 20 16 17 18 19 5 21 22 23 24 15
  4 20 6 7 8 9 15 11 12 13 14 0 16 17 18 19 10 21 22 23 24 5 1 2 3
  7 8 9 20 11 12 13 14 5 16 17 18 19 0 21 22 23 24 15 1 2 3 4 10 6
  0 11 12 13 14 20 16 17 18 19 10 21 22 23 24 5 1 2 3 4 15 6 7 8 9
  13 14 5 16 17 18 19 0 21 22 23 24 10 1 2 3 4 20 6 7 8 9 15 11 12
  16 17 18 19 5 21 22 23 24 15 1 2 3 4 10 6 7 8 9 0 11 12 13 14 20
  19 10 21 22 23 24 5 1 2 3 4 20 6 7 8 9 15 11 12 13 14 0 16 17 18
  22 23 24 15 1 2 3 4 10 6 7 8 9 20 11 12 13 14 5 16 17 18 19 0 21
		

Crossrefs

A369379 Number of Dabbaghian-Wu pandiagonal Latin squares of order 2n+1 with the first row in order.

Original entry on oeis.org

1, 0, 0, 4, 0, 0, 72, 0, 0, 108, 0, 0, 4, 0, 0, 180, 0, 3, 216, 0, 0, 252, 0, 0, 264, 0, 0, 0, 0, 0, 360, 0, 5, 396, 0, 0, 432, 0, 0, 468, 0, 0, 0, 0, 0, 868, 0, 5, 576, 0
Offset: 1

Views

Author

Eduard I. Vatutin, Jan 22 2024

Keywords

Comments

A pandiagonal Latin square is a Latin square in which the diagonal, antidiagonal and all broken diagonals and antidiagonals are transversals.
A Dabbaghian-Wu pandiagonal Latin square (see A368027) is a special type of pandiagonal Latin square (see A342306). Such squares are constructed from cyclic diagonal Latin squares (see A338562) for prime orders n=6k+1 (see Dabbaghian and Wu article) using a polynomial algorithm based on permutation of some values in Latin square. For other orders (25, 35, 49, ...) this algorithm also ensures correct pandiagonal Latin squares.

Examples

			n=13=6*2+1 (prime order):
.
 0  1  2  3  4  5  6  7  8  9 10 11 12
 2  3  0  1 11 12  8  4 10  7  5  6  9
 4 10 11  2  8  1  3  0 12  6  9  7  5
11  5  9  7 10  0 12  1  3  2  8  4  6
 8  7 10  5  9  6 11  2  0  4  3 12  1
12  0  4  6  7  2  9 10  5 11  1  8  3
 1  6 12  8  3  4  5 11  9 10  7  2  0
 9  2  3  4 12  8  1  6  7  5  0 10 11
10 11  5  0  1  3  7  8  4 12  6  9  2
 5  9  1 11  2 10  0 12  6  8  4  3  7
 6  8  7 10  0 11  2  9  1  3 12  5  4
 7  4  6 12  5  9 10  3  2  0 11  1  8
 3 12  8  9  6  7  4  5 11  1  2  0 10
.
n=19=6*3+1 (prime order):
.
 0  1  2  3  4  5  6  7  8  9 10 11 12
 2  3  0  1 11 12  8  4 10  7  5  6  9
 4 10 11  2  8  1  3  0 12  6  9  7  5
11  5  9  7 10  0 12  1  3  2  8  4  6
 8  7 10  5  9  6 11  2  0  4  3 12  1
12  0  4  6  7  2  9 10  5 11  1  8  3
 1  6 12  8  3  4  5 11  9 10  7  2  0
 9  2  3  4 12  8  1  6  7  5  0 10 11
10 11  5  0  1  3  7  8  4 12  6  9  2
 5  9  1 11  2 10  0 12  6  8  4  3  7
 6  8  7 10  0 11  2  9  1  3 12  5  4
 7  4  6 12  5  9 10  3  2  0 11  1  8
 3 12  8  9  6  7  4  5 11  1  2  0 10
.
n=25=6*4+1 (nonprime order):
.
 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
 3  4 15  6  7  8  9  5 11 12 13 14  0 16 17 18 19 10 21 22 23 24 20  1  2
 6  7  8  9 10 11 12 13 14 15 16 17 18 19  0 21 22 23 24  5  1  2  3  4 20
 9  5 11 12 13 14 10 16 17 18 19 20 21 22 23 24  0  1  2  3  4 15  6  7  8
12 13 14  0 16 17 18 19 10 21 22 23 24  5  1  2  3  4 20  6  7  8  9 15 11
15 16 17 18 19 20 21 22 23 24  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14
18 19 10 21 22 23 24 20  1  2  3  4 15  6  7  8  9  5 11 12 13 14  0 16 17
21 22 23 24  5  1  2  3  4 20  6  7  8  9 10 11 12 13 14 15 16 17 18 19  0
24  0  1  2  3  4 15  6  7  8  9  5 11 12 13 14 10 16 17 18 19 20 21 22 23
 2  3  4 20  6  7  8  9 15 11 12 13 14  0 16 17 18 19 10 21 22 23 24  5  1
 5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  0  1  2  3  4
 8  9  5 11 12 13 14  0 16 17 18 19 10 21 22 23 24 20  1  2  3  4 15  6  7
11 12 13 14 15 16 17 18 19  0 21 22 23 24  5  1  2  3  4 20  6  7  8  9 10
14 10 16 17 18 19 20 21 22 23 24  0  1  2  3  4 15  6  7  8  9  5 11 12 13
17 18 19 10 21 22 23 24  5  1  2  3  4 20  6  7  8  9 15 11 12 13 14  0 16
20 21 22 23 24  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19
23 24 20  1  2  3  4 15  6  7  8  9  5 11 12 13 14  0 16 17 18 19 10 21 22
 1  2  3  4 20  6  7  8  9 10 11 12 13 14 15 16 17 18 19  0 21 22 23 24  5
 4 15  6  7  8  9  5 11 12 13 14 10 16 17 18 19 20 21 22 23 24  0  1  2  3
 7  8  9 15 11 12 13 14  0 16 17 18 19 10 21 22 23 24  5  1  2  3  4 20  6
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  0  1  2  3  4  5  6  7  8  9
13 14  0 16 17 18 19 10 21 22 23 24 20  1  2  3  4 15  6  7  8  9  5 11 12
16 17 18 19  0 21 22 23 24  5  1  2  3  4 20  6  7  8  9 10 11 12 13 14 15
19 20 21 22 23 24  0  1  2  3  4 15  6  7  8  9  5 11 12 13 14 10 16 17 18
22 23 24  5  1  2  3  4 20  6  7  8  9 15 11 12 13 14  0 16 17 18 19 10 21
		

Crossrefs

A369380 Number of main classes of diagonal Latin squares containing Dabbaghian-Wu pandiagonal Latin squares of order 2n+1.

Original entry on oeis.org

1, 0, 0, 1, 0, 0, 8, 0, 0, 18, 0, 0
Offset: 1

Views

Author

Eduard I. Vatutin, Jan 22 2024

Keywords

Comments

A pandiagonal Latin square is a Latin square in which the diagonal, antidiagonal and all broken diagonals and antidiagonals are transversals.
A Dabbaghian-Wu pandiagonal Latin square (see A368027) is a special type of pandiagonal Latin square (see A342306). Such squares are constructed from cyclic diagonal Latin squares (see A338562) for prime orders n=6k+1 (see Dabbaghian and Wu article) using a polynomial algorithm based on permutation of some values in Latin square. For other orders (25, 35, 49, ...) this algorithm also ensures correct pandiagonal Latin squares.

Crossrefs

A370672 Number of ways of arranging 2n+1 nonattacking queens on a 2n+1 X 2n+1 toroidal board using knight moves.

Original entry on oeis.org

1, 0, 10, 28, 0, 88, 130, 0, 238, 304, 0, 460, 250, 0, 754, 868, 0, 280, 1258, 0, 1558, 1720, 0, 2068, 1372, 0, 2650, 880, 0, 3304, 3538, 0, 1300, 4288, 0, 4828, 5110, 0, 2464, 6004, 0, 6640, 2380, 0, 7654, 3640, 0
Offset: 0

Views

Author

Eduard I. Vatutin, Feb 25 2024

Keywords

Comments

All solutions of this type can be found using a knight moving with some displacements dx and dy starting from some cell with coordinates (x,y): (x,y) -> (x+dx,y+dy) -> (x+2*dx,y+2*dy) -> ... -> (x,y) (all operations modulo n). For n <= 11 all solutions of n nonattacking queens on n X n a toroidal board problem are solutions of this type, for n >= 13 some solutions are not of this type (see A051906 for examples).

Examples

			For n=2*2+1=5 there are 10 solutions:
.
+-----------+ +-----------+ +-----------+ +-----------+ +-----------+
| Q . . . . | | Q . . . . | | . Q . . . | | . Q . . . | | . . Q . . |
| . . Q . . | | . . . Q . | | . . . Q . | | . . . . Q | | Q . . . . |
| . . . . Q | | . Q . . . | | Q . . . . | | . . Q . . | | . . . Q . |
| . Q . . . | | . . . . Q | | . . Q . . | | Q . . . . | | . Q . . . |
| . . . Q . | | . . Q . . | | . . . . Q | | . . . Q . | | . . . . Q |
+-----------+ +-----------+ +-----------+ +-----------+ +-----------+
.
+-----------+ +-----------+ +-----------+ +-----------+ +-----------+
| . . Q . . | | . . . Q . | | . . . Q . | | . . . . Q | | . . . . Q |
| . . . . Q | | Q . . . . | | . Q . . . | | . Q . . . | | . . Q . . |
| . Q . . . | | . . Q . . | | . . . . Q | | . . . Q . | | Q . . . . |
| . . . Q . | | . . . . Q | | . . Q . . | | Q . . . . | | . . . Q . |
| Q . . . . | | . Q . . . | | Q . . . . | | . . Q . . | | . Q . . . |
+-----------+ +-----------+ +-----------+ +-----------+ +-----------+
.
so a(2)=10.
		

Crossrefs

Formula

a(n) = A123565(2*n+1) * (2*n+1).
a(n) = A338562(n) / (2n)!. - Eduard I. Vatutin, Mar 13 2024

A366333 a(n) is the number of distinct numbers of diagonal transversals that a semicyclic diagonal Latin square of order 2n+1 can have.

Original entry on oeis.org

1, 0, 1, 1, 0, 2, 20, 0, 271, 1208, 0
Offset: 0

Views

Author

Eduard I. Vatutin, Oct 07 2023

Keywords

Comments

A horizontally semicyclic diagonal Latin square is a square where each row r(i) is a cyclic shift of the first row r(0) by some value d(i) (see example). A vertically semicyclic diagonal Latin square is a square where each column c(i) is a cyclic shift of the first column c(0) by some value d(i). Cyclic diagonal Latin squares (see A338562) fall under the definition of vertically and horizontally semicyclic diagonal Latin squares simultaneously, in this type of squares each row r(i) is obtained from the previous one r(i-1) using cyclic shift by some value d.
Semicyclic diagonal Latin squares do not exist for even orders n.

Examples

			For n=6*2+1=13 the number of diagonal transversals that a semicyclic diagonal Latin square of order 13 may have is 127339, 127830, 128489, 128519, 128533, 128608, 128751, 128818, 128861, 129046, 129059, 129171, 129243, 129286, 129353, 129474, 129641, 129657, 130323 or 131106. Since there are 20 distinct values, a(6)=20.
		

Crossrefs

Previous Showing 11-18 of 18 results.