# A097679 (b-file synthesized from sequence entry) 0 1 1 4 2 16 3 64 4 280 5 1600 6 12160 7 102400 8 880000 9 8358400 10 94720000 11 1189888000 12 15213952000 13 204285952000 14 3092697088000 15 51351519232000 16 869951500288000 17 15148619579392000 18 287722152460288000 19 5927812334878720000