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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 30 |
| 7 | 106 |
| 8 | 420 |
| 9 | 1818 |
| 10 | 8530 |
| 11 | 43430 |
| 12 | 240208 |
| 13 | 1439850 |
| 14 | 9304070 |
| 15 | 64403138 |
| 16 | 474740644 |
| 17 | 3708087226 |
| 18 | 30560873242 |
| 19 | 264810927102 |
| 20 | 2404843230640 |
| 21 | 22825442299962 |
| 22 | 225893502009054 |
| 23 | 2326337105570074 |
| 24 | 24888766556869700 |
| 25 | 276246054635709850 |
[1,1,1,2,4,10,30,106,420,1818,8530,43430,240208, 1439850,9304070,64403138,474740644,3708087226, 30560873242,264810927102,2404843230640, 22825442299962,225893502009054,2326337105570074, 24888766556869700,276246054635709850] |