# A375664 (b-file synthesized from sequence entry) 0 1 1 0 2 0 3 12 4 0 5 120 6 2160 7 1680 8 120960 9 1481760 10 6350400 11 240166080 12 2754259200 13 31152401280 14 894303970560 15 11769588230400 16 228232766361600 17 5845147711603200 18 98290727395660800 19 2502848611354291200 20 63417766359467520000 21 1376904298716724377600