# A025966 (b-file synthesized from sequence entry) 0 1 1 20 2 260 3 2800 4 27216 5 248640 6 2182720 7 18656000 8 156544256 9 1296655360 10 10641146880 11 86744985600 12 703688298496 13 5688011079680 14 45855653642240 15 368956766617600 16 2964331947687936 17 23790756829593600