# A100621 (b-file synthesized from sequence entry) 0 1 1 2 2 6 3 8 4 90 5 288 6 840 7 17280 8 28350 9 89600 10 598752 11 17418240 12 63063000 13 402361344000 14 5003856000 15 295206912 16 976924698750 17 342372925440000 18 15209113920000 19 5377993912811520000 20 96852084769440 21 89903156428800000 22 37556196837868800000 23 73570956727261593600000