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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 23 |
| 4 | 203 |
| 5 | 1606 |
| 6 | 18435 |
| 7 | 221778 |
| 8 | 2773763 |
| 9 | 33297380 |
| 10 | 375158732 |
| 11 | 3907656327 |
| 12 | 37504171766 |
| 13 | 331785257145 |
| 14 | 2712509085687 |
| 15 | 20560611034067 |
| 16 | 144992583036707 |
| 17 | 954428916508309 |
| 18 | 5882732966056385 |
| 19 | 34048050206744705 |
[1,1,7,23,203,1606,18435,221778,2773763,33297380, 375158732,3907656327,37504171766,331785257145, 2712509085687,20560611034067,144992583036707, 954428916508309,5882732966056385, 34048050206744705] |