# A002018 (b-file synthesized from sequence entry) 0 1 1 1 2 4 3 33 4 480 5 11010 6 367560 7 16854390 8 1016930880 9 78124095000 10 7446314383200 11 862332613342200 12 119261328828364800 13 19415283189746043600 14 3675162134109650184000 15 800409618620667941886000 16 198730589981586780813696000 17 55800304882692417053710704000