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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 17 |
| 5 | 186 |
| 6 | 1552 |
| 7 | 19251 |
| 8 | 218745 |
| 9 | 3156250 |
| 10 | 45156986 |
| 11 | 759167421 |
| 12 | 13081892540 |
| 13 | 253473235549 |
| 14 | 5105981313721 |
| 15 | 112582925665944 |
| 16 | 2594769928231945 |
| 17 | 64333665380435714 |
| 18 | 1669153290412964962 |
| 19 | 46044314009644973181 |
| 20 | 1327862271936474871422 |
| 21 | 40379182417276002300375 |
[1,1,4,17,186,1552,19251,218745,3156250,45156986, 759167421,13081892540,253473235549,5105981313721, 112582925665944,2594769928231945, 64333665380435714,1669153290412964962, 46044314009644973181,1327862271936474871422, 40379182417276002300375] |