# A003807 (b-file synthesized from sequence entry) 1 168 2 5616 3 20160 4 372000 5 1876896 6 16482816 7 42456960 8 212427600 9 270178272 10 1425715200 11 6950204928 12 5644682640 13 78156525216 14 50778000000 15 282027786768 16 499631102880 17 283991644800 18 1098404364288