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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 15 |
| 4 | 27 |
| 5 | 354 |
| 6 | 893 |
| 7 | 2127 |
| 8 | 2133 |
| 9 | 2427 |
| 10 | 2649 |
| 11 | 4098 |
| 12 | 4107 |
| 13 | 6189 |
| 14 | 19721 |
| 15 | 124064 |
| 16 | 140287 |
| 17 | 1200685 |
| 18 | 17347808 |
| 19 | 18209035 |
| 20 | 32738176 |
| 21 | 35033632 |
[1,2,15,27,354,893,2127,2133,2427,2649,4098,4107, 6189,19721,124064,140287,1200685,17347808, 18209035,32738176,35033632] |