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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 4 |
| 4 | 9 |
| 5 | 22 |
| 6 | 61 |
| 7 | 200 |
| 8 | 689 |
| 9 | 3054 |
| 10 | 12110 |
| 11 | 61132 |
| 12 | 274264 |
| 13 | 1515134 |
| 14 | 7498195 |
| 15 | 44301928 |
| 16 | 238206692 |
| 17 | 1490114770 |
| 18 | 8605537805 |
| 19 | 56612534420 |
| 20 | 348083793872 |
| 21 | 2396294898646 |
| 22 | 15577794980189 |
| 23 | 111781094032984 |
| 24 | 763986810923430 |
| 25 | 5695585712379834 |
[1,2,3,4,9,22,61,200,689,3054,12110,61132,274264, 1515134,7498195,44301928,238206692,1490114770, 8605537805,56612534420,348083793872,2396294898646, 15577794980189,111781094032984,763986810923430, 5695585712379834] |