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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 28 |
| 4 | 352 |
| 5 | 7696 |
| 6 | 296704 |
| 7 | 19845568 |
| 8 | 2325071872 |
| 9 | 472050401536 |
| 10 | 167325747134464 |
| 11 | 102717666720160768 |
| 12 | 109887628080679616512 |
| 13 | 203517277347030338768896 |
| 14 | 656102983404750860283019264 |
| 15 | 3660938644168893995628877692928 |
[1,1,4,28,352,7696,296704,19845568,2325071872, 472050401536,167325747134464,102717666720160768, 109887628080679616512,203517277347030338768896, 656102983404750860283019264, 3660938644168893995628877692928] |