a(n) = Product_{k=1..n} k^(2k - 1 - n).

A001142

a(n) = Product_{k=1..n} k^(2k - 1 - n).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =9a(4) =96a(5) =2500a(6) =162000a(7) =26471025a(8) =11014635520

External references