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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 21 |
| 3 | 56 |
| 4 | 147 |
| 5 | 385 |
| 6 | 1008 |
| 7 | 2639 |
| 8 | 6909 |
| 9 | 18088 |
| 10 | 47355 |
| 11 | 123977 |
| 12 | 324576 |
| 13 | 849751 |
| 14 | 2224677 |
| 15 | 5824280 |
| 16 | 15248163 |
| 17 | 39920209 |
| 18 | 104512464 |
| 19 | 273617183 |
| 20 | 716339085 |
| 21 | 1875400072 |
| 22 | 4909861131 |
| 23 | 12854183321 |
[1,7,21,56,147,385,1008,2639,6909,18088,47355, 123977,324576,849751,2224677,5824280,15248163, 39920209,104512464,273617183,716339085,1875400072, 4909861131,12854183321] |