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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 8 |
| 5 | 25 |
| 6 | 72 |
| 7 | 259 |
| 8 | 1024 |
| 9 | 4113 |
| 10 | 18720 |
| 11 | 89859 |
| 12 | 451200 |
| 13 | 2452905 |
| 14 | 13870976 |
| 15 | 82466115 |
| 16 | 517341184 |
| 17 | 3364642465 |
| 18 | 22907884032 |
| 19 | 162289204995 |
| 20 | 1190546278400 |
| 21 | 9080010901689 |
| 22 | 71557772290048 |
| 23 | 582825476943747 |
| 24 | 4904509780131840 |
[0,1,2,3,8,25,72,259,1024,4113,18720,89859,451200, 2452905,13870976,82466115,517341184,3364642465, 22907884032,162289204995,1190546278400, 9080010901689,71557772290048,582825476943747, 4904509780131840] |