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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 85 |
| 4 | 519 |
| 5 | 3330 |
| 6 | 22135 |
| 7 | 151089 |
| 8 | 1052805 |
| 9 | 7458236 |
| 10 | 53554548 |
| 11 | 388913046 |
| 12 | 2851368587 |
| 13 | 21076979445 |
| 14 | 156907929177 |
| 15 | 1175381112901 |
| 16 | 8853057357159 |
| 17 | 67007699270040 |
| 18 | 509390314298820 |
| 19 | 3887605401119964 |
| 20 | 29775366104932044 |
[1,3,15,85,519,3330,22135,151089,1052805,7458236, 53554548,388913046,2851368587,21076979445, 156907929177,1175381112901,8853057357159, 67007699270040,509390314298820,3887605401119964, 29775366104932044] |