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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 4 |
| 5 | 10 |
| 6 | 20 |
| 7 | 35 |
| 8 | 6776 |
| 9 | 60564 |
| 10 | 352920 |
| 11 | 1663365 |
| 12 | 126625180 |
| 13 | 2361079006 |
| 14 | 27334747804 |
| 15 | 245495250455 |
| 16 | 11174333090480 |
| 17 | 328952158255400 |
| 18 | 6245314009946736 |
| 19 | 90576650639967369 |
| 20 | 3209305759254634740 |
| 21 | 122557203047084965810 |
| 22 | 3365068665450300234580 |
[0,0,0,0,4,10,20,35,6776,60564,352920,1663365, 126625180,2361079006,27334747804,245495250455, 11174333090480,328952158255400,6245314009946736, 90576650639967369,3209305759254634740, 122557203047084965810,3365068665450300234580] |