A242997 - cp's OEIS frontend

A242997 a(n) is the order of the group of invertible elements in the semigroup M whose elements are the closed binary operations on an n-point set S and whose operation (on operations, in this case) is given by x AB y = (x B y) A (y B x) for operations A and B on S and points x and y in S.

n	a(n)
1	1
2	4
3	288
4	1105920
5	445906944000
6	30851909057249280000
7	540013176648715369394995200000
8	3299903381977999900396941913809223680000000
9	9276369213749813701818662527515163802639831924736000000000

[1, 4, 288, 1105920, 445906944000, 30851909057249280000, 540013176648715369394995200000, 3299903381977999900396941913809223680000000, 9276369213749813701818662527515163802639831924736000000000]

cp's OEIS Frontend

A242997 a(n) is the order of the group of invertible elements in the semigroup M whose elements are the closed binary operations on an n-point set S and whose operation (on operations, in this case) is given by x AB y = (x B y) A (y B x) for operations A and B on S and points x and y in S.

Table of values

List of values