n | a(n) |
---|---|
0 | 0 |
1 | 1 |
2 | 0 |
3 | 2 |
4 | 4 |
5 | 20 |
6 | 100 |
7 | 620 |
8 | 4420 |
9 | 35900 |
10 | 326980 |
11 | 3301820 |
12 | 36614980 |
13 | 442386620 |
14 | 5784634180 |
15 | 81393657020 |
16 | 1226280710980 |
17 | 19696509177020 |
18 | 335990918918980 |
19 | 6066382786809020 |
20 | 115578717622022980 |
21 | 2317323290554617020 |
22 | 48773618881154822980 |
23 | 1075227108896452857020 |
[0,1,0,2,4,20,100,620,4420,35900,326980,3301820, 36614980,442386620,5784634180,81393657020, 1226280710980,19696509177020,335990918918980, 6066382786809020,115578717622022980, 2317323290554617020,48773618881154822980, 1075227108896452857020] |