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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 17 |
| 4 | 112 |
| 5 | 769 |
| 6 | 7088 |
| 7 | 66387 |
| 8 | 763600 |
| 9 | 9164721 |
| 10 | 126474672 |
| 11 | 1820139771 |
| 12 | 29458146408 |
| 13 | 494179557897 |
| 14 | 9100332756552 |
| 15 | 174762729699459 |
| 16 | 3612983961103776 |
| 17 | 77711328568772193 |
| 18 | 1784695351000035744 |
| 19 | 42494646959739633771 |
[1,1,4,17,112,769,7088,66387,763600,9164721, 126474672,1820139771,29458146408,494179557897, 9100332756552,174762729699459,3612983961103776, 77711328568772193,1784695351000035744, 42494646959739633771] |