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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 9 |
| 3 | 55 |
| 4 | 322 |
| 5 | 1946 |
| 6 | 11664 |
| 7 | 69980 |
| 8 | 419912 |
| 9 | 2519416 |
| 10 | 15116544 |
| 11 | 90699280 |
| 12 | 544195552 |
| 13 | 3265173536 |
| 14 | 19591041024 |
| 15 | 117546246080 |
| 16 | 705277476992 |
| 17 | 4231664861056 |
| 18 | 25389989167104 |
| 19 | 152339935002880 |
| 20 | 914039610015232 |
| 21 | 5484237660094976 |
| 22 | 32905425960566784 |
| 23 | 197432555763399680 |
[1,9,55,322,1946,11664,69980,419912,2519416, 15116544,90699280,544195552,3265173536, 19591041024,117546246080,705277476992, 4231664861056,25389989167104,152339935002880, 914039610015232,5484237660094976, 32905425960566784,197432555763399680] |