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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1155 |
| 4 | 759759 |
| 5 | 103786510 |
| 6 | 4767856260 |
| 7 | 107118740001 |
| 8 | 1465350136810 |
| 9 | 13956101513964 |
| 10 | 100946621623995 |
| 11 | 588405869207695 |
| 12 | 2882842751900001 |
| 13 | 12245455022841690 |
| 14 | 46164185630256694 |
| 15 | 157281327978056205 |
| 16 | 491245336843482180 |
| 17 | 1422828159652548376 |
| 18 | 3857444027819847045 |
| 19 | 9864873410828916699 |
| 20 | 23951146853875652515 |
| 21 | 55509091777214287590 |
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