# A353992 (b-file synthesized from sequence entry) 1 1 2 7 3 41 4 314 5 2194 6 22764 7 195348 8 2374224 9 27940176 10 384636960 11 4673720160 12 95522440320 13 1323221996160 14 23481816503040 15 489968947641600 16 10853692580505600 17 190580382936115200 18 5408424680491929600 19 105077728210820198400 20 3399507785578641408000