The number of partial isometries (of an n-chain) of fix zero (fix of alpha = 0). Equivalently, the number of partial derangement isometries (of an n-chain).

A183159

The number of partial isometries (of an n-chain) of fix zero (fix of alpha = 0). Equivalently, the number of partial derangement isometries (of an n-chain).

Terms

    a(0) =1a(1) =1a(2) =4a(3) =12a(4) =38a(5) =90a(6) =220a(7) =460a(8) =1018a(9) =2022a(10) =4304a(11) =8376a(12) =17566a(13) =33922a(14) =70756a(15) =136260a(16) =283682a(17) =545790a(18) =1135576a(19) =2184112a(20) =4543366a(21) =8737626a(22) =18174764a(23) =34951932a(24) =72700618a(25) =139809430a(26) =290804320a(27) =559239720a(28) =1163219438

External references