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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 11 |
| 4 | 12 |
| 5 | 70 |
| 6 | 408 |
| 7 | 2378 |
| 8 | 13860 |
| 9 | 80782 |
| 10 | 470832 |
| 11 | 2744210 |
| 12 | 15994428 |
| 13 | 93222358 |
| 14 | 543339720 |
| 15 | 3166815962 |
| 16 | 18457556052 |
| 17 | 107578520350 |
| 18 | 627013566048 |
| 19 | 3654502875938 |
| 20 | 21300003689580 |
| 21 | 124145519261542 |
| 22 | 723573111879672 |
| 23 | 4217293152016490 |
| 24 | 24580185800219268 |
[0,2,11,12,70,408,2378,13860,80782,470832,2744210, 15994428,93222358,543339720,3166815962, 18457556052,107578520350,627013566048, 3654502875938,21300003689580,124145519261542, 723573111879672,4217293152016490, 24580185800219268] |