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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 15 |
| 5 | 42 |
| 6 | 77 |
| 7 | 180 |
| 8 | 345 |
| 9 | 806 |
| 10 | 1457 |
| 11 | 3276 |
| 12 | 5985 |
| 13 | 13462 |
| 14 | 24257 |
| 15 | 54060 |
| 16 | 97665 |
| 17 | 217686 |
| 18 | 391937 |
| 19 | 871596 |
| 20 | 1570305 |
| 21 | 3492182 |
| 22 | 6286337 |
| 23 | 13972140 |
| 24 | 25155585 |
| 25 | 55911766 |
| 26 | 100642817 |
| 27 | 223660716 |
| 28 | 402612225 |
| 29 | 894735702 |
| 30 | 1610530817 |
| 31 | 3578997420 |
| 32 | 6442287105 |
| 33 | 14316361046 |
[0,1,2,6,15,42,77,180,345,806,1457,3276,5985, 13462,24257,54060,97665,217686,391937,871596, 1570305,3492182,6286337,13972140,25155585, 55911766,100642817,223660716,402612225,894735702, 1610530817,3578997420,6442287105,14316361046] |