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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 55 |
| 6 | 239 |
| 7 | 1199 |
| 8 | 6810 |
| 9 | 43108 |
| 10 | 300731 |
| 11 | 2291162 |
| 12 | 18923688 |
| 13 | 168402163 |
| 14 | 1606199354 |
| 15 | 16345042652 |
| 16 | 176758631046 |
| 17 | 2024225038882 |
| 18 | 24471719797265 |
| 19 | 311446235344127 |
| 20 | 4162172487402027 |
| 21 | 58275220793611957 |
| 22 | 853045299274146032 |
[1,1,2,5,15,55,239,1199,6810,43108,300731,2291162, 18923688,168402163,1606199354,16345042652, 176758631046,2024225038882,24471719797265, 311446235344127,4162172487402027, 58275220793611957,853045299274146032] |