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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 20 |
| 4 | 147 |
| 5 | 670 |
| 6 | 2239 |
| 7 | 6138 |
| 8 | 14531 |
| 9 | 30904 |
| 10 | 60369 |
| 11 | 110300 |
| 12 | 190671 |
| 13 | 314910 |
| 14 | 500247 |
| 15 | 768810 |
| 16 | 110300 |
| 17 | 190671 |
| 18 | 314910 |
| 19 | 500247 |
| 20 | 768810 |
| 21 | 1147959 |
| 22 | 1671648 |
[0,0,1,20,147,670,2239,6138,14531,30904,60369, 110300,190671,314910,500247,768810,110300,190671, 314910,500247,768810,1147959,1671648] |