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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 58 |
| 5 | 515 |
| 6 | 6117 |
| 7 | 89015 |
| 8 | 1582412 |
| 9 | 33346657 |
| 10 | 816759195 |
| 11 | 22980062928 |
| 12 | 733407740393 |
| 13 | 26280164467356 |
| 14 | 1048777166376622 |
| 15 | 46274709506560769 |
| 16 | 2242998363098170350 |
| 17 | 118779992677414890453 |
| 18 | 6838446632281205146327 |
| 19 | 426147448479639862008434 |
| 20 | 28631211803547719170094520 |
[1,1,2,9,58,515,6117,89015,1582412,33346657, 816759195,22980062928,733407740393,26280164467356, 1048777166376622,46274709506560769, 2242998363098170350,118779992677414890453, 6838446632281205146327,426147448479639862008434, 28631211803547719170094520] |