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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 18 |
| 2 | 88 |
| 3 | 438 |
| 4 | 2188 |
| 5 | 10938 |
| 6 | 54688 |
| 7 | 273438 |
| 8 | 1367188 |
| 9 | 6835938 |
| 10 | 34179688 |
| 11 | 170898438 |
| 12 | 854492188 |
| 13 | 4272460938 |
| 14 | 21362304688 |
| 15 | 106811523438 |
| 16 | 534057617188 |
| 17 | 2670288085938 |
| 18 | 13351440429688 |
| 19 | 66757202148438 |
| 20 | 333786010742188 |
| 21 | 1668930053710938 |
[4,18,88,438,2188,10938,54688,273438,1367188, 6835938,34179688,170898438,854492188,4272460938, 21362304688,106811523438,534057617188, 2670288085938,13351440429688,66757202148438, 333786010742188,1668930053710938] |