# A002178 (b-file synthesized from sequence entry) 1 1 2 4 3 3 4 32 5 75 6 216 7 3577 8 5888 9 15741 10 106300 11 13486539 12 9903168 13 56280729661 14 710986864 15 265553865 16 127626606592 17 450185515446285 18 1848730221900 19 603652082270808125 20 187926090380000 21 9545933933230947