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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 74 |
| 6 | 372 |
| 7 | 2116 |
| 8 | 13376 |
| 9 | 91944 |
| 10 | 651888 |
| 11 | 5780164 |
| 12 | 51776784 |
| 13 | 517517604 |
| 14 | 5477813312 |
| 15 | 59576133472 |
| 16 | 755631632616 |
[1,2,6,24,74,372,2116,13376,91944,651888,5780164, 51776784,517517604,5477813312,59576133472, 755631632616] |