# A163145 (b-file synthesized from sequence entry) 0 1 1 21 2 420 3 8400 4 167790 5 3351600 6 66948210 7 1337288400 8 26712295890 9 533577313500 10 10658190898110 11 212897044846500 12 4252612111884990 13 84945799915397400 14 1696789816099808010 15 33893325895893882600 16 677018172425014524090 17 13523417772619230573300