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| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 9 |
| 5 | 56 |
| 6 | 301 |
| 7 | 1506 |
| 8 | 7258 |
| 9 | 34322 |
| 10 | 161039 |
| 11 | 755145 |
| 12 | 3556269 |
| 13 | 16876326 |
| 14 | 80881483 |
| 15 | 392014244 |
| 16 | 1922785012 |
| 17 | 9545380884 |
| 18 | 47947476888 |
| 19 | 243553779646 |
| 20 | 1250097073918 |
| 21 | 6477850149236 |
| 22 | 33857970839030 |
| 23 | 178339124650000 |
| 24 | 945852940569120 |
[1,9,56,301,1506,7258,34322,161039,755145,3556269, 16876326,80881483,392014244,1922785012,9545380884, 47947476888,243553779646,1250097073918, 6477850149236,33857970839030,178339124650000, 945852940569120] |