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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 11 |
| 3 | 42 |
| 4 | 136 |
| 5 | 400 |
| 6 | 1104 |
| 7 | 2912 |
| 8 | 7424 |
| 9 | 18432 |
| 10 | 44800 |
| 11 | 107008 |
| 12 | 251904 |
| 13 | 585728 |
| 14 | 1347584 |
| 15 | 3072000 |
| 16 | 6946816 |
| 17 | 15597568 |
| 18 | 34799616 |
| 19 | 77201408 |
| 20 | 170393600 |
| 21 | 374341632 |
| 22 | 818937856 |
| 23 | 1784676352 |
| 24 | 3875536896 |
| 25 | 8388608000 |
| 26 | 18102616064 |
| 27 | 38956695552 |
| 28 | 83617644544 |
| 29 | 179046449152 |
[0,2,11,42,136,400,1104,2912,7424,18432,44800, 107008,251904,585728,1347584,3072000,6946816, 15597568,34799616,77201408,170393600,374341632, 818937856,1784676352,3875536896,8388608000, 18102616064,38956695552,83617644544,179046449152] |