A279200 Number of square permutations of 2n things.

1, 2, 20, 504, 21032, 1293418

Offset: 0

Author

N. J. A. Sloane, Dec 15 2016

Keywords

• nonn
• more

Examples

			The 20 square permutations of order 4 are 1234, 1243, 1423, 1324, 1342, 4132, 3124, 3142, 3412, 4312, 2134, 2143, 2413, 4213, 2314, 2431, 4231, 3241, 3421, 4321.
		

Links

• Samuele Giraudo, S. Vialette, Unshuffling Permutations, arXiv preprint arXiv:1601.05962 [cs.DS], 2016.

Crossrefs

Cf. A191755 (square binary words).