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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 20 |
| 5 | 44 |
| 6 | 98 |
| 7 | 218 |
| 8 | 485 |
| 9 | 1079 |
| 10 | 2400 |
| 11 | 5339 |
| 12 | 11878 |
| 13 | 26426 |
| 14 | 58791 |
| 15 | 130795 |
| 16 | 290986 |
| 17 | 647370 |
| 18 | 1440233 |
| 19 | 3204151 |
| 20 | 7128419 |
| 21 | 15858914 |
| 22 | 35282038 |
| 23 | 78493533 |
| 24 | 174628085 |
| 25 | 388502937 |
| 26 | 864319917 |
| 27 | 1922891303 |
| 28 | 4277942565 |
| 29 | 9517330782 |
| 30 | 21173632847 |
[1,2,4,9,20,44,98,218,485,1079,2400,5339,11878, 26426,58791,130795,290986,647370,1440233,3204151, 7128419,15858914,35282038,78493533,174628085, 388502937,864319917,1922891303,4277942565, 9517330782,21173632847] |