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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 25 |
| 5 | 129 |
| 6 | 713 |
| 7 | 4373 |
| 8 | 30289 |
| 9 | 235041 |
| 10 | 1998001 |
| 11 | 18226117 |
| 12 | 176364969 |
| 13 | 1803064033 |
| 14 | 19463340729 |
| 15 | 221691818005 |
| 16 | 2658751147297 |
| 17 | 33458500940993 |
| 18 | 440140082161121 |
| 19 | 6032572875160069 |
| 20 | 85936355674437561 |
| 21 | 1270176766188103105 |
| 22 | 19453176663852208937 |
[1,1,1,5,25,129,713,4373,30289,235041,1998001, 18226117,176364969,1803064033,19463340729, 221691818005,2658751147297,33458500940993, 440140082161121,6032572875160069, 85936355674437561,1270176766188103105, 19453176663852208937] |