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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 30 |
| 4 | 115 |
| 5 | 510 |
| 6 | 2602 |
| 7 | 15133 |
| 8 | 99367 |
| 9 | 729962 |
| 10 | 5949393 |
| 11 | 53392902 |
| 12 | 524077321 |
| 13 | 5592200388 |
| 14 | 64520858034 |
| 15 | 801031071955 |
| 16 | 10654883235991 |
| 17 | 151253483735767 |
| 18 | 2283450321888155 |
| 19 | 36544617881242655 |
| 20 | 618220383026770560 |
[1,3,9,30,115,510,2602,15133,99367,729962,5949393, 53392902,524077321,5592200388,64520858034, 801031071955,10654883235991,151253483735767, 2283450321888155,36544617881242655, 618220383026770560] |