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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 36 |
| 3 | 324 |
| 4 | 1996 |
| 5 | 10154 |
| 6 | 47448 |
| 7 | 211888 |
| 8 | 920744 |
| 9 | 3930286 |
| 10 | 16570608 |
| 11 | 69240296 |
| 12 | 287379592 |
| 13 | 1186575444 |
| 14 | 4879222736 |
| 15 | 19997163520 |
| 16 | 81735122832 |
| 17 | 333327346838 |
| 18 | 1356783786272 |
| 19 | 5513802056888 |
| 20 | 22376476701512 |
| 21 | 90701190829388 |
[1,36,324,1996,10154,47448,211888,920744,3930286, 16570608,69240296,287379592,1186575444,4879222736, 19997163520,81735122832,333327346838, 1356783786272,5513802056888,22376476701512, 90701190829388] |