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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 265 |
| 7 | 579 |
| 8 | 1265 |
| 9 | 2783 |
| 10 | 6208 |
| 11 | 13909 |
| 12 | 31337 |
| 13 | 70985 |
| 14 | 161545 |
| 15 | 369024 |
| 16 | 845825 |
| 17 | 1944295 |
| 18 | 4480285 |
| 19 | 10345391 |
| 20 | 23930320 |
| 21 | 55435605 |
| 22 | 128577253 |
| 23 | 298529333 |
| 24 | 693718721 |
| 25 | 1613210120 |
| 26 | 3753680073 |
| 27 | 8738534315 |
| 28 | 20351593033 |
| 29 | 47413960239 |
| 30 | 110493496000 |
[1,1,2,6,24,120,265,579,1265,2783,6208,13909, 31337,70985,161545,369024,845825,1944295,4480285, 10345391,23930320,55435605,128577253,298529333, 693718721,1613210120,3753680073,8738534315, 20351593033,47413960239,110493496000] |