# A002677 (b-file synthesized from sequence entry) 1 1 2 4 3 40 4 12096 5 604800 6 760320 7 217945728000 8 697426329600 9 16937496576000 10 30964207376793600 11 187333454629601280000 12 111407096483020800000 13 1814811575069725360128000000 14 10162944820390462016716800000