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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 80 |
| 6 | 810 |
| 7 | 10857 |
| 8 | 174944 |
| 9 | 3243060 |
| 10 | 67859010 |
| 11 | 1586109305 |
| 12 | 41085509652 |
| 13 | 1170954002946 |
| 14 | 36469499267474 |
| 15 | 1233416773419495 |
| 16 | 45037748851872240 |
| 17 | 1766375778253548392 |
| 18 | 74067278799492363330 |
| 19 | 3306928891056821667045 |
| 20 | 156635771633727023132300 |
[1,1,3,12,80,810,10857,174944,3243060,67859010, 1586109305,41085509652,1170954002946, 36469499267474,1233416773419495,45037748851872240, 1766375778253548392,74067278799492363330, 3306928891056821667045,156635771633727023132300] |