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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 21 |
| 3 | 107 |
| 4 | 273 |
| 5 | 1911 |
| 6 | 5189 |
| 7 | 28123 |
| 8 | 65793 |
| 9 | 460551 |
| 10 | 1381653 |
| 11 | 7039851 |
| 12 | 17829905 |
| 13 | 124809335 |
| 14 | 340873541 |
| 15 | 1840690907 |
| 16 | 4295032833 |
| 17 | 30065229831 |
| 18 | 90195689493 |
| 19 | 459568513131 |
| 20 | 1172543963409 |
| 21 | 8207807743863 |
| 22 | 22286925370437 |
[1,7,21,107,273,1911,5189,28123,65793,460551, 1381653,7039851,17829905,124809335,340873541, 1840690907,4295032833,30065229831,90195689493, 459568513131,1172543963409,8207807743863, 22286925370437] |