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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 3 |
| 6 | 15 |
| 7 | 57 |
| 8 | 167 |
| 9 | 423 |
| 10 | 1099 |
| 11 | 3391 |
| 12 | 11855 |
| 13 | 41149 |
| 14 | 134185 |
| 15 | 418859 |
| 16 | 1313861 |
| 17 | 4285349 |
| 18 | 14456605 |
| 19 | 49097477 |
| 20 | 164889821 |
| 21 | 548126215 |
| 22 | 1824046555 |
| 23 | 6131204373 |
| 24 | 20817947419 |
| 25 | 70988707243 |
| 26 | 241907381783 |
| 27 | 823235370195 |
| 28 | 2804366824235 |
[1,1,1,1,3,15,57,167,423,1099,3391,11855,41149, 134185,418859,1313861,4285349,14456605,49097477, 164889821,548126215,1824046555,6131204373, 20817947419,70988707243,241907381783,823235370195, 2804366824235] |