| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 5 |
| 2 | 28 |
| 3 | 210 |
| 4 | 1848 |
| 5 | 18018 |
| 6 | 188760 |
| 7 | 2085798 |
| 8 | 24018280 |
| 9 | 285817532 |
| 10 | 3493769552 |
| 11 | 43672119400 |
| 12 | 556315613280 |
| 13 | 7202300350500 |
| 14 | 94561966954800 |
| 15 | 1256886144107550 |
| 16 | 16888191533829000 |
| 17 | 229116465142280100 |
| 18 | 3135277944052254000 |
| 19 | 43238333101156993800 |
| 20 | 600502564063273528800 |
[2,5,28,210,1848,18018,188760,2085798,24018280, 285817532,3493769552,43672119400,556315613280, 7202300350500,94561966954800,1256886144107550, 16888191533829000,229116465142280100, 3135277944052254000,43238333101156993800, 600502564063273528800] |