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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 8 |
| 3 | 21 |
| 4 | 54 |
| 5 | 138 |
| 6 | 350 |
| 7 | 885 |
| 8 | 2230 |
| 9 | 5610 |
| 10 | 14088 |
| 11 | 35346 |
| 12 | 88596 |
| 13 | 221952 |
| 14 | 555738 |
| 15 | 1391061 |
| 16 | 3480870 |
| 17 | 8708610 |
| 18 | 21783680 |
| 19 | 54483510 |
| 20 | 136254964 |
| 21 | 340729788 |
| 22 | 852000828 |
| 23 | 2130354786 |
| 24 | 5326563004 |
[1,3,8,21,54,138,350,885,2230,5610,14088,35346, 88596,221952,555738,1391061,3480870,8708610, 21783680,54483510,136254964,340729788,852000828, 2130354786,5326563004] |