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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 28 |
| 4 | 91 |
| 5 | 303 |
| 6 | 1028 |
| 7 | 3542 |
| 8 | 12363 |
| 9 | 43628 |
| 10 | 155414 |
| 11 | 558144 |
| 12 | 2018750 |
| 13 | 7347281 |
| 14 | 26888610 |
| 15 | 98888730 |
| 16 | 365292555 |
| 17 | 1354757040 |
| 18 | 5042499990 |
| 19 | 18830130360 |
| 20 | 70527871530 |
| 21 | 264886906830 |
| 22 | 997372693824 |
| 23 | 3764155637772 |
| 24 | 14236915323806 |
[1,3,9,28,91,303,1028,3542,12363,43628,155414, 558144,2018750,7347281,26888610,98888730, 365292555,1354757040,5042499990,18830130360, 70527871530,264886906830,997372693824, 3764155637772,14236915323806] |