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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 33 |
| 4 | 231 |
| 5 | 1680 |
| 6 | 12722 |
| 7 | 99174 |
| 8 | 790695 |
| 9 | 6417782 |
| 10 | 52854210 |
| 11 | 440569659 |
| 12 | 3709925170 |
| 13 | 31512765744 |
| 14 | 269690266146 |
| 15 | 2323196695551 |
| 16 | 20128333751349 |
| 17 | 175286209221924 |
| 18 | 1533444732404226 |
| 19 | 13469998501882377 |
| 20 | 118760989817062512 |
| 21 | 1050602774154917980 |
| 22 | 9322513339131716088 |
[1,0,6,33,231,1680,12722,99174,790695,6417782, 52854210,440569659,3709925170,31512765744, 269690266146,2323196695551,20128333751349, 175286209221924,1533444732404226, 13469998501882377,118760989817062512, 1050602774154917980,9322513339131716088] |