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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 12 |
| 7 | 30 |
| 8 | 86 |
| 9 | 253 |
| 10 | 748 |
| 11 | 2274 |
| 12 | 7152 |
| 13 | 22890 |
| 14 | 74189 |
| 15 | 243342 |
| 16 | 808599 |
| 17 | 2716549 |
| 18 | 9213420 |
| 19 | 31498358 |
| 20 | 108483093 |
| 21 | 376145636 |
| 22 | 1312463081 |
| 23 | 4605569378 |
| 24 | 16245866825 |
[1,1,1,1,2,5,12,30,86,253,748,2274,7152,22890, 74189,243342,808599,2716549,9213420,31498358, 108483093,376145636,1312463081,4605569378, 16245866825] |