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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 45 |
| 4 | 153 |
| 5 | 702 |
| 6 | 2754 |
| 7 | 11259 |
| 8 | 50058 |
| 9 | 224046 |
| 10 | 990873 |
| 11 | 4304988 |
| 12 | 18175185 |
| 13 | 77439321 |
| 14 | 327135510 |
| 15 | 1408297995 |
| 16 | 6302244447 |
| 17 | 29140976502 |
| 18 | 135628856406 |
| 19 | 622855827801 |
| 20 | 2796140431278 |
| 21 | 12364271615628 |
| 22 | 54378167114070 |
| 23 | 240937280782164 |
| 24 | 1080881256295566 |
[1,3,9,45,153,702,2754,11259,50058,224046,990873, 4304988,18175185,77439321,327135510,1408297995, 6302244447,29140976502,135628856406,622855827801, 2796140431278,12364271615628,54378167114070, 240937280782164,1080881256295566] |