# A006147 (b-file synthesized from sequence entry) 1 1 2 24 3 900 4 40352 5 1994322 6 104816880 7 5747466920 8 325077729600 9 18826860841119 10 1110900168420264 11 66547088543789532 12 4036419643768799328 13 247405021070280491110 14 15299980644645295780560 15 953473460271200881693560 16 59817824263728235912396224