# A167532 (b-file synthesized from sequence entry) 0 1 1 2 2 2 3 8 4 20 5 112 6 432 7 3200 8 16704 9 154688 10 1017920 11 11333888 12 90011264 13 1172330496 14 10908526592 15 162802835456 16 1737036006400 17 29235365490688 18 351847501606912 19 6593866787569664 20 88364197074231296 21 1825016315965767680