a(n) = (n+1)*(2*n)!/(2^n*n!) = (n+1)*(2n-1)!!.
A001193
a(n) = (n+1)*(2*n)!/(2^n*n!) = (n+1)*(2n-1)!!.
Terms
- a(0) =1a(1) =2a(2) =9a(3) =60a(4) =525a(5) =5670a(6) =72765a(7) =1081080a(8) =18243225a(9) =344594250a(10) =7202019825a(11) =164991726900
External references
- oeis: A001193