# A229039 (b-file synthesized from sequence entry) 0 1 1 3 2 7 3 24 4 108 5 600 6 3960 7 30240 8 262080 9 2540160 10 27216000 11 319334400 12 4071513600 13 56043187200 14 828193766400 15 13076743680000 16 219689293824000 17 3912561709056000 18 73627297615872000 19 1459741204905984000 20 30411275102208000000 21 664182248232222720000