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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 65 |
| 5 | 353 |
| 6 | 2025 |
| 7 | 12074 |
| 8 | 74083 |
| 9 | 464708 |
| 10 | 2966647 |
| 11 | 19211268 |
| 12 | 125890754 |
| 13 | 833242554 |
| 14 | 5562338802 |
| 15 | 37406660537 |
| 16 | 253185542824 |
| 17 | 1723428340232 |
| 18 | 11790556480270 |
| 19 | 81026845851661 |
| 20 | 559086953351167 |
| 21 | 3871831119088196 |
[1,1,3,13,65,353,2025,12074,74083,464708,2966647, 19211268,125890754,833242554,5562338802, 37406660537,253185542824,1723428340232, 11790556480270,81026845851661,559086953351167, 3871831119088196] |