a(n) is the number of partial bijections (or subpermutations) of an n-element set without fixed points (also called partial derangements).

A144085

a(n) is the number of partial bijections (or subpermutations) of an n-element set without fixed points (also called partial derangements).

Terms

    a(0) =1a(1) =1a(2) =4a(3) =18a(4) =108a(5) =780a(6) =6600a(7) =63840a(8) =693840a(9) =8361360a(10) =110557440a(11) =1590351840a(12) =24713156160a(13) =412393101120

External references