# A162743 (b-file synthesized from sequence entry) 0 1 1 6 2 30 3 135 4 600 5 2640 6 11610 7 51000 8 224040 9 984060 10 4322400 11 18985440 12 83390760 13 366280800 14 1608831840 15 7066542960 16 31038691200 17 136332618240 18 598819808160 19 2630222793600 20 11552844224640 21 50744069991360