# A227726 (b-file synthesized from sequence entry) 0 1 1 4 2 20 3 112 4 660 5 4004 6 24752 7 155040 8 980628 9 6249100 10 40060020 11 258048960 12 1668903600 13 10829900592 14 70480305440 15 459823234112 16 3006465218196 17 19694758782300 18 129235131438140 19 849311959095600 20 5589126007740660 21 36825913869817380 22 242910890642347200