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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 21 |
| 4 | 78 |
| 5 | 1540 |
| 6 | 30381 |
| 7 | 112575 |
| 8 | 2220778 |
| 9 | 43809480 |
| 10 | 162333171 |
| 11 | 3202360435 |
| 12 | 63173239878 |
| 13 | 234084320106 |
| 14 | 4617801526591 |
| 15 | 91095768094695 |
| 16 | 337549427259780 |
| 17 | 6658866598983886 |
| 18 | 131360034419310411 |
| 19 | 486746040024282753 |
| 20 | 9602081017933237120 |
| 21 | 189421078536877518066 |
| 22 | 701887452165588470145 |
[0,1,21,78,1540,30381,112575,2220778,43809480, 162333171,3202360435,63173239878,234084320106, 4617801526591,91095768094695,337549427259780, 6658866598983886,131360034419310411, 486746040024282753,9602081017933237120, 189421078536877518066,701887452165588470145] |