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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 33 |
| 4 | 424 |
| 5 | 7445 |
| 6 | 166176 |
| 7 | 4505053 |
| 8 | 143787904 |
| 9 | 5282091081 |
| 10 | 219531404800 |
| 11 | 10184792907641 |
| 12 | 521761503753216 |
| 13 | 29254578504622237 |
| 14 | 1781920872844693504 |
| 15 | 117169936148978011125 |
| 16 | 8272258025961978167296 |
[0,1,4,33,424,7445,166176,4505053,143787904, 5282091081,219531404800,10184792907641, 521761503753216,29254578504622237, 1781920872844693504,117169936148978011125, 8272258025961978167296] |