# A280889 (b-file synthesized from sequence entry) 0 1 1 1 2 4 3 75 4 56 5 6930 6 28512 7 2849847 8 972400 9 693870606 10 99936200 11 63488350926 12 475814969280 13 166184959669300 14 497980728000 15 78877488833249175 16 1489333512849120 17 1116126129558913110 18 1597083864660900000 19 4467282986266589095530 20 107279471180408841600