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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 27 |
| 5 | 163 |
| 6 | 1268 |
| 7 | 12344 |
| 8 | 145653 |
| 9 | 2036149 |
| 10 | 33192790 |
| 11 | 622384730 |
| 12 | 13263528351 |
| 13 | 318121600695 |
| 14 | 8517247764136 |
| 15 | 252725694989612 |
| 16 | 8258153081400857 |
| 17 | 295515712276222953 |
| 18 | 11523986940937975402 |
| 19 | 487562536078882116718 |
| 20 | 22291094729329088403299 |
| 21 | 1097336766599161926448779 |
[1,1,2,6,27,163,1268,12344,145653,2036149, 33192790,622384730,13263528351,318121600695, 8517247764136,252725694989612,8258153081400857, 295515712276222953,11523986940937975402, 487562536078882116718,22291094729329088403299, 1097336766599161926448779] |