# A131705 (b-file synthesized from sequence entry) 0 0 1 1 2 16 3 144 4 1536 5 7200 6 51840 7 282240 8 1474560 9 7464960 10 55296000 11 200724480 12 1051066368 13 6167715840 14 21459271680 15 114960384000 16 523197480960 17 2214903398400 18 9311791104000 19 41500698624000 20 183936614400000