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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 15 |
| 6 | 32 |
| 7 | 126 |
| 8 | 351 |
| 9 | 1094 |
| 10 | 3321 |
| 11 | 9801 |
| 12 | 29768 |
| 13 | 88452 |
| 14 | 266085 |
| 15 | 797162 |
| 16 | 2390391 |
| 17 | 7175547 |
| 18 | 21516800 |
| 19 | 64573362 |
| 20 | 193700403 |
| 21 | 581130734 |
| 22 | 1743421725 |
| 23 | 5230147077 |
| 24 | 15690706952 |
| 25 | 47071500840 |
| 26 | 141215033961 |
| 27 | 423644304722 |
| 28 | 1270932117003 |
| 29 | 3812799539655 |
[1,0,1,2,3,15,32,126,351,1094,3321,9801,29768, 88452,266085,797162,2390391,7175547,21516800, 64573362,193700403,581130734,1743421725, 5230147077,15690706952,47071500840,141215033961, 423644304722,1270932117003,3812799539655] |