# A104680 (b-file synthesized from sequence entry) 0 792 1 13728 2 123552 3 772200 4 3775200 5 15402816 6 54609984 7 172931616 8 498841200 9 1330243200 10 3316739712 11 7801876368 12 17439488352 13 37263864000 14 76488984000 15 151448188320 16 290275694280 17 540192201120 18 978609060000 19 1729734435000 20 2988981103680 21 5058275713920