# A123899 (b-file synthesized from sequence entry) 0 1 1 2 2 3 3 12 4 60 5 360 6 252 7 2016 8 36288 9 362880 10 4989600 11 11975040 12 622702080 13 8717829120 14 65383718400 15 5230697472000 16 2736057139200 17 49249028505600 18 30411275102208 19 608225502044160 20 25545471085854720000