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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 64 |
| 4 | 548 |
| 5 | 5608 |
| 6 | 68936 |
| 7 | 973600 |
| 8 | 15700352 |
| 9 | 283559424 |
| 10 | 5685644928 |
| 11 | 125227712256 |
| 12 | 3007981305600 |
| 13 | 78237291643392 |
| 14 | 2191215982262784 |
| 15 | 65744691667064832 |
| 16 | 2103999919044163584 |
| 17 | 71538799576401408000 |
| 18 | 2575460412946013810688 |
| 19 | 97868678834373255069696 |
| 20 | 3914776163575281528889344 |
[1,2,10,64,548,5608,68936,973600,15700352, 283559424,5685644928,125227712256,3007981305600, 78237291643392,2191215982262784,65744691667064832, 2103999919044163584,71538799576401408000, 2575460412946013810688,97868678834373255069696, 3914776163575281528889344] |