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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 8 |
| 2 | 44 |
| 3 | 209 |
| 4 | 900 |
| 5 | 3780 |
| 6 | 15272 |
| 7 | 61720 |
| 8 | 247052 |
| 9 | 990704 |
| 10 | 3964037 |
| 11 | 15861216 |
| 12 | 63442960 |
| 13 | 253791069 |
| 14 | 1015179869 |
| 15 | 4060805808 |
[1,8,44,209,900,3780,15272,61720,247052,990704, 3964037,15861216,63442960,253791069,1015179869, 4060805808] |