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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 7 |
| 5 | 13 |
| 6 | 20 |
| 7 | 38 |
| 8 | 69 |
| 9 | 129 |
| 10 | 222 |
| 11 | 407 |
| 12 | 726 |
| 13 | 1313 |
| 14 | 2318 |
| 15 | 4146 |
| 16 | 7432 |
| 17 | 13296 |
| 18 | 23759 |
| 19 | 42458 |
| 20 | 75714 |
[1,1,2,3,7,13,20,38,69,129,222,407,726,1313,2318, 4146,7432,13296,23759,42458,75714] |