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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 7 |
| 6 | 24 |
| 7 | 60 |
| 8 | 240 |
| 9 | 930 |
| 10 | 4701 |
| 11 | 26637 |
| 12 | 178569 |
| 13 | 1339529 |
| 14 | 11187064 |
| 15 | 101871881 |
| 16 | 1002594996 |
| 17 | 10574095327 |
| 18 | 118850827173 |
| 19 | 1417140114336 |
| 20 | 17860018997346 |
| 21 | 237160827107408 |
| 22 | 3309078044759285 |
| 23 | 48396906463199522 |
| 24 | 740331404753448181 |
| 25 | 11821525310570525197 |
[1,0,1,1,4,7,24,60,240,930,4701,26637,178569, 1339529,11187064,101871881,1002594996,10574095327, 118850827173,1417140114336,17860018997346, 237160827107408,3309078044759285, 48396906463199522,740331404753448181, 11821525310570525197] |