# A280078 (b-file synthesized from sequence entry) 1 1 2 4 3 20 4 220 5 1540 6 30800 7 277200 8 7207200 9 129729600 10 3632428800 11 47221574400 12 2597186592000 13 38957798880000 14 1402480759680000 15 49086826588800000 16 2797949115561600000 17 53161033195670400000 18 3827594390088268800000 19 80379482191853644800000