0,2
Table of n, a(n) for n=0..5.
Samuele Giraudo, S. Vialette, Unshuffling Permutations, arXiv preprint arXiv:1601.05962 [cs.DS], 2016.
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.
Cf. A191755 (square binary words).
Sequence in context: A012340 A279839 A279837 * A277414 A296789 A168136
Adjacent sequences: A279197 A279198 A279199 * A279201 A279202 A279203
nonn,more
N. J. A. Sloane, Dec 15 2016
approved
