138940401600domain: NAppears in sequencesa(n) = (3*n)!/(2^n*n!).at n=6A166334a(0) = a(1) = 1, a(n) = n! / a(n-2).at n=22A214916a(n) = (2*n)!/a(n-1), with a(0)=1.at n=11A372986