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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 21 |
| 3 | 93 |
| 4 | 378 |
| 5 | 1519 |
| 6 | 6126 |
| 7 | 24747 |
| 8 | 99964 |
| 9 | 403743 |
| 10 | 1630662 |
| 11 | 6586087 |
| 12 | 26600572 |
| 13 | 107437031 |
| 14 | 433927396 |
| 15 | 1752589551 |
| 16 | 7078534592 |
| 17 | 28589495207 |
| 18 | 115470119764 |
| 19 | 466372299261 |
| 20 | 1883631211124 |
| 21 | 7607798625811 |
| 22 | 30727139997676 |
| 23 | 124103854340837 |
[4,21,93,378,1519,6126,24747,99964,403743,1630662, 6586087,26600572,107437031,433927396,1752589551, 7078534592,28589495207,115470119764,466372299261, 1883631211124,7607798625811,30727139997676, 124103854340837] |