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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 6 |
| 5 | 57 |
| 6 | 678 |
| 7 | 9375 |
| 8 | 146334 |
| 9 | 2555228 |
| 10 | 49498389 |
| 11 | 1054882116 |
| 12 | 24545326598 |
| 13 | 619415271672 |
| 14 | 16854164945997 |
| 15 | 491956017936245 |
| 16 | 15335174679459134 |
| 17 | 508475723159116576 |
| 18 | 17870522292434937714 |
| 19 | 663618269365250877446 |
| 20 | 25964529622925026990819 |
| 21 | 1067602511902741954478695 |
[1,6,57,678,9375,146334,2555228,49498389, 1054882116,24545326598,619415271672, 16854164945997,491956017936245,15335174679459134, 508475723159116576,17870522292434937714, 663618269365250877446,25964529622925026990819, 1067602511902741954478695] |