a(n) = Product_{i=1..floor(n/2)} (2n-i)*(2n+i).

A249056

a(n) = Product_{i=1..floor(n/2)} (2n-i)*(2n+i).

Terms

    a(0) =1a(1) =1a(2) =15a(3) =35a(4) =3780a(5) =9504a(6) =2702700a(7) =7001280a(8) =3809332800a(9) =10027987200

External references