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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 56 |
| 4 | 640 |
| 5 | 8158 |
| 6 | 111258 |
| 7 | 1588544 |
| 8 | 23446248 |
| 9 | 354855218 |
| 10 | 5477342222 |
| 11 | 85893429256 |
| 12 | 1364577254040 |
| 13 | 21916000458014 |
| 14 | 355251287893170 |
| 15 | 5804407209709312 |
| 16 | 95493879511032240 |
| 17 | 1580592247322440642 |
| 18 | 26301843121772151254 |
| 19 | 439764358275666481496 |
| 20 | 7384252698468635017936 |
| 21 | 124469446338979722639294 |
[1,6,56,640,8158,111258,1588544,23446248, 354855218,5477342222,85893429256,1364577254040, 21916000458014,355251287893170,5804407209709312, 95493879511032240,1580592247322440642, 26301843121772151254,439764358275666481496, 7384252698468635017936,124469446338979722639294] |