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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 3 |
| 5 | 15 |
| 6 | 105 |
| 7 | 525 |
| 8 | 3255 |
| 9 | 17703 |
| 10 | 112455 |
| 11 | 669735 |
| 12 | 4485195 |
| 13 | 29023995 |
| 14 | 205768563 |
| 15 | 1432735395 |
| 16 | 10728177915 |
| 17 | 79665069435 |
| 18 | 627587657595 |
| 19 | 4933313794683 |
| 20 | 40724759240235 |
| 21 | 336819780949995 |
| 22 | 2902978545030795 |
| 23 | 25135723046974155 |
| 24 | 225455477000793963 |
[0,0,0,3,15,105,525,3255,17703,112455,669735, 4485195,29023995,205768563,1432735395,10728177915, 79665069435,627587657595,4933313794683, 40724759240235,336819780949995,2902978545030795, 25135723046974155,225455477000793963] |