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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 18 |
| 3 | 93 |
| 4 | 468 |
| 5 | 2343 |
| 6 | 11718 |
| 7 | 58593 |
| 8 | 292968 |
| 9 | 1464843 |
| 10 | 7324218 |
| 11 | 36621093 |
| 12 | 183105468 |
| 13 | 915527343 |
| 14 | 4577636718 |
| 15 | 22888183593 |
| 16 | 114440917968 |
| 17 | 572204589843 |
| 18 | 2861022949218 |
| 19 | 14305114746093 |
| 20 | 71525573730468 |
| 21 | 357627868652343 |
[0,3,18,93,468,2343,11718,58593,292968,1464843, 7324218,36621093,183105468,915527343,4577636718, 22888183593,114440917968,572204589843, 2861022949218,14305114746093,71525573730468, 357627868652343] |