# A277407 (b-file synthesized from sequence entry) 0 1 1 1 2 3 3 19 4 220 5 4196 6 120876 7 4915212 8 268194816 9 18903020544 10 1671209210880 11 181064295924480 12 23589442167333120 13 3638090042721918720 14 655483159341216541440 15 136420837710333144595200 16 32478481518550347674419200 17 8770206330674425311097651200 18 2666047809138871800854163456000 19 906320525390421790143785781657600 20 342508343836409428996994343026688000