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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 72 |
| 5 | 724 |
| 6 | 9184 |
| 7 | 142080 |
| 8 | 2587392 |
| 9 | 54290256 |
| 10 | 1289277440 |
| 11 | 34191270752 |
| 12 | 1001513996288 |
| 13 | 32113767783616 |
| 14 | 1118831623585792 |
| 15 | 42084750888906240 |
| 16 | 1699836383279448064 |
| 17 | 73377208318764134656 |
| 18 | 3371248736937012363264 |
| 19 | 164251735270613613412864 |
[0,1,2,10,72,724,9184,142080,2587392,54290256, 1289277440,34191270752,1001513996288, 32113767783616,1118831623585792,42084750888906240, 1699836383279448064,73377208318764134656, 3371248736937012363264,164251735270613613412864] |