a(n) = n * (2*n - 1)!! - Sum_{k=0..n-1} a(k) * (2*n - 2*k - 1)!!.
A004208
a(n) = n * (2*n - 1)!! - Sum_{k=0..n-1} a(k) * (2*n - 2*k - 1)!!.
Terms
- a(0) =1a(1) =5a(2) =37a(3) =353a(4) =4081a(5) =55205a(6) =854197a(7) =14876033a(8) =288018721a(9) =6138913925a(10) =142882295557
External references
- oeis: A004208