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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 21 |
| 6 | 36 |
| 7 | 78 |
| 8 | 1770 |
| 9 | 2628 |
| 10 | 330078 |
| 11 | 1160526 |
| 12 | 1106921826 |
| 13 | 27467109390 |
| 14 | 3405462502501956 |
| 15 | 464491597897585896 |
| 16 | 35168538277628662422146736 |
| 17 | 113107978211040574688911417114776 |
| 18 | 158163225773885113469535108323447683287341095656 |
[1,3,6,15,21,36,78,1770,2628,330078,1160526, 1106921826,27467109390,3405462502501956, 464491597897585896,35168538277628662422146736, 113107978211040574688911417114776, 158163225773885113469535108323447683287341095656] |