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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 30 |
| 4 | 138 |
| 5 | 562 |
| 6 | 2700 |
| 7 | 11364 |
| 8 | 55756 |
| 9 | 238874 |
| 10 | 1186616 |
| 11 | 5140518 |
| 12 | 25745026 |
| 13 | 112379472 |
| 14 | 566088616 |
| 15 | 2484706008 |
| 16 | 12570242776 |
| 17 | 55405777178 |
| 18 | 281236520744 |
| 19 | 1243692265890 |
| 20 | 6329700657110 |
| 21 | 28065758573186 |
| 22 | 143148739542708 |
| 23 | 636106122212964 |
[1,2,8,30,138,562,2700,11364,55756,238874,1186616, 5140518,25745026,112379472,566088616,2484706008, 12570242776,55405777178,281236520744, 1243692265890,6329700657110,28065758573186, 143148739542708,636106122212964] |