Hi,

I define a subset of permutations as a subset where there is no more then 1 element the same on the same place

For example a permutation of 4 elements

1 2 3 4

1 3 4 2

1 4 2 3

2 1 4 3

2 3 1 4

..

there are 12 of them (I think)

For a permutation of 6 elements

2 4 3 6 5 2

2 5 6 1 2 3

2 6 5 2 1 4

3 1 3 5 2 4

3 2 4 6 1 3

.....

maybe 24 of them?

My questions are :

1) can be calculated how many there are for n elements

2) how can the set be constructed?

Thanks for any response