a(n) = (2*n)!/core(n!)^2/(n+1) where core(x) is the squarefree part of x.

A072118

a(n) = (2*n)!/core(n!)^2/(n+1) where core(x) is the squarefree part of x.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =224a(4) =672a(5) =2737152a(6) =8895744a(7) =474439680a(8) =130660687872

External references