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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 36 |
| 4 | 176 |
| 5 | 940 |
| 6 | 5568 |
| 7 | 37128 |
| 8 | 280992 |
| 9 | 2410812 |
| 10 | 23250080 |
| 11 | 249164344 |
| 12 | 2934303264 |
| 13 | 37617633976 |
| 14 | 521009920256 |
| 15 | 7748175156240 |
| 16 | 123095897716800 |
| 17 | 2080205257723740 |
| 18 | 37253560076385120 |
| 19 | 704703668205036120 |
| 20 | 14039778681732928800 |
| 21 | 293831851498842784680 |
[1,2,8,36,176,940,5568,37128,280992,2410812, 23250080,249164344,2934303264,37617633976, 521009920256,7748175156240,123095897716800, 2080205257723740,37253560076385120, 704703668205036120,14039778681732928800, 293831851498842784680] |