# A365975 (b-file synthesized from sequence entry) 0 1 1 1 2 2 3 6 4 30 5 180 6 1260 7 10800 8 104760 9 1130760 10 13776480 11 184044960 12 2670220080 13 42222280320 14 718144004160 15 13061603808000 16 254036916144000 17 5247117638294400 18 114652672773408000 19 2647321293055507200 20 64330669872690566400 21 1640738743703289331200