# A066165 (b-file synthesized from sequence entry) 3 3 4 8 5 30 6 234 7 1680 8 13040 9 119448 10 1212120 11 13412520 12 161968872 13 2118607920 14 29813747040 15 449227822680 16 7216747374720 17 123128587713600 18 2223511629522624 19 42370586275466880 20 849664985938704000 21 17886165587251839360 22 394366490810199895680 23 9088843342633833461760