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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 16 |
| 3 | 208 |
| 4 | 3776 |
| 5 | 88064 |
| 6 | 2509312 |
| 7 | 84484096 |
| 8 | 3281641472 |
| 9 | 144454565888 |
| 10 | 7106455404544 |
| 11 | 386388342341632 |
| 12 | 23008661588148224 |
| 13 | 1489229440694091776 |
| 14 | 104099447480095080448 |
| 15 | 7815625800589565231104 |
| 16 | 627246405151556410277888 |
| 17 | 53587201970725717343731712 |
| 18 | 4855511229494719127650041856 |
[1,2,16,208,3776,88064,2509312,84484096, 3281641472,144454565888,7106455404544, 386388342341632,23008661588148224, 1489229440694091776,104099447480095080448, 7815625800589565231104,627246405151556410277888, 53587201970725717343731712, 4855511229494719127650041856] |