140229804000domain: NAppears in sequencesa(n) = 0!*1!*2!*...*(n-1)! *(n^2)! *(n*(n-1))^2 / 2*n!*(n+1)!*...*(2*n-1)!at n=4A181200a(n)=0!*1!*2!*3!*4!*(5*n)!*10*n*(n-1) / ((n)!*(n+1)!*(n+2)!*(n+3)!*(n+4)!).at n=4A181203T(n,k) = 0!*1!*2!*...*(k-1)! *(n*k)! *k*(k-1)*n*(n-1) / 2*n!*(n+1)!*...*(n+k-1)!at n=40A181204