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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 9 |
| 3 | 37 |
| 4 | 137 |
| 5 | 487 |
| 6 | 1749 |
| 7 | 5901 |
| 8 | 19695 |
| 9 | 63832 |
| 10 | 202905 |
| 11 | 632689 |
| 12 | 1941394 |
| 13 | 5860868 |
| 14 | 17448558 |
| 15 | 51255292 |
| 16 | 148726841 |
| 17 | 426605755 |
| 18 | 1210569740 |
| 19 | 3400427281 |
| 20 | 9460683203 |
| 21 | 26083933370 |
| 22 | 71300381025 |
| 23 | 193313191005 |
| 24 | 520057831035 |
| 25 | 1388722752205 |
| 26 | 3682100198763 |
[1,1,9,37,137,487,1749,5901,19695,63832,202905, 632689,1941394,5860868,17448558,51255292, 148726841,426605755,1210569740,3400427281, 9460683203,26083933370,71300381025,193313191005, 520057831035,1388722752205,3682100198763] |