# A001757 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 9 4 54 5 450 6 4500 7 55125 8 771750 9 12502350 10 225042300 11 4538353050 12 99843767100 13 2410513805700 14 62673358948200 15 1762688220418125 16 52880646612543750 17 1698056319002793750 18 57733914846094987500 19 2084194325944029048750