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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 28 |
| 2 | 148 |
| 3 | 621 |
| 4 | 2420 |
| 5 | 9152 |
| 6 | 34164 |
| 7 | 126854 |
| 8 | 470288 |
| 9 | 1744200 |
| 10 | 6478088 |
| 11 | 24107105 |
| 12 | 89908380 |
[0,28,148,621,2420,9152,34164,126854,470288, 1744200,6478088,24107105,89908380] |