n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 20 |
3 | 112 |
4 | 676 |
5 | 4312 |
6 | 28704 |
7 | 197600 |
8 | 1397060 |
9 | 10090676 |
10 | 74152456 |
11 | 552666448 |
12 | 4167528000 |
13 | 31736182776 |
14 | 243698432960 |
15 | 1884809367456 |
16 | 14668777816708 |
17 | 114789815231560 |
18 | 902661488046900 |
19 | 7129068237647408 |
20 | 56524456978032904 |
21 | 449752267499647104 |
[1,4,20,112,676,4312,28704,197600,1397060, 10090676,74152456,552666448,4167528000, 31736182776,243698432960,1884809367456, 14668777816708,114789815231560,902661488046900, 7129068237647408,56524456978032904, 449752267499647104] |