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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 64 |
| 5 | 1280 |
| 6 | 707584 |
| 7 | 28672 |
| 8 | 59260928 |
| 9 | 2874867712 |
| 10 | 45773225984 |
| 11 | 896021823488 |
| 12 | 991382852337664 |
| 13 | 143497256501248 |
| 14 | 1593799350268461056 |
| 15 | 2312797281748024033280 |
| 16 | 8277820436597920759808 |
| 17 | 11071085050982544965632 |
| 18 | 452092922822895257024443973632 |
[1,4,16,64,1280,707584,28672,59260928,2874867712, 45773225984,896021823488,991382852337664, 143497256501248,1593799350268461056, 2312797281748024033280,8277820436597920759808, 11071085050982544965632, 452092922822895257024443973632] |