One half of third column of triangle A075181.

A075183

One half of third column of triangle A075181.

Terms

    a(0) =1a(1) =11a(2) =105a(3) =1020a(4) =10500a(5) =115920a(6) =1375920a(7) =17539200a(8) =239500800a(9) =3492720000a(10) =54226972800a(11) =893577484800

External references