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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 4 |
| 3 | 11 |
| 4 | 25 |
| 5 | 62 |
| 6 | 162 |
| 7 | 433 |
| 8 | 1175 |
| 9 | 3229 |
| 10 | 9042 |
| 11 | 25549 |
| 12 | 73050 |
| 13 | 210356 |
| 14 | 610041 |
| 15 | 1779830 |
| 16 | 5218745 |
| 17 | 15372304 |
| 18 | 45455747 |
| 19 | 134882577 |
| 20 | 401480918 |
| 21 | 1198344171 |
| 22 | 3585783711 |
| 23 | 10754085805 |
| 24 | 32319203663 |
| 25 | 97312548674 |
| 26 | 293515297707 |
| 27 | 886720888966 |
| 28 | 2682778745396 |
| 29 | 8127887397064 |
[0,2,4,11,25,62,162,433,1175,3229,9042,25549, 73050,210356,610041,1779830,5218745,15372304, 45455747,134882577,401480918,1198344171, 3585783711,10754085805,32319203663,97312548674, 293515297707,886720888966,2682778745396, 8127887397064] |