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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 24 |
| 3 | 216 |
| 4 | 2184 |
| 5 | 23592 |
| 6 | 267144 |
| 7 | 3128472 |
| 8 | 37582680 |
| 9 | 460564632 |
| 10 | 5735093832 |
| 11 | 72359126376 |
| 12 | 923021734344 |
| 13 | 11884281689688 |
| 14 | 154243249784856 |
| 15 | 2015831498613720 |
| 16 | 26506024201097352 |
| 17 | 350404606655241768 |
| 18 | 4654501489433893512 |
| 19 | 62092356103141330584 |
| 20 | 831534637662059617368 |
[1,3,24,216,2184,23592,267144,3128472,37582680, 460564632,5735093832,72359126376,923021734344, 11884281689688,154243249784856,2015831498613720, 26506024201097352,350404606655241768, 4654501489433893512,62092356103141330584, 831534637662059617368] |