Consider the n pairs (1,2), ..., (2n-1,2n); a(n) is the number of permutations of [ 2n ] with no two fixed points for any pair.

A177840

Consider the n pairs (1,2), ..., (2n-1,2n); a(n) is the number of permutations of [ 2n ] with no two fixed points for any pair.

Terms

    a(0) =1a(1) =1a(2) =21a(3) =653a(4) =37577a(5) =3434169a(6) =457819549a(7) =83900098309

External references