# A046105 (b-file synthesized from sequence entry) 0 1 1 2 2 16 3 120 4 882 5 6468 6 47680 7 354224 8 2652688 9 20008864 10 151853312 11 1158365824 12 8873772392 13 68219456080 14 526025997824 15 4066475337152 16 31505967787522 17 244574907064964 18 1901855959279776 19 14811829930479600 20 115514550050260068 21 901993060739459720