a(n) = RisingFactorial(2*n, n) = A124320(2*n, n).

A352601

a(n) = RisingFactorial(2*n, n) = A124320(2*n, n).

Terms

    a(0) =1a(1) =2a(2) =20a(3) =336a(4) =7920a(5) =240240a(6) =8910720a(7) =390700800a(8) =19769460480

External references