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.

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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
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