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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 11 |
| 5 | 30 |
| 6 | 108 |
| 7 | 406 |
| 8 | 1764 |
| 9 | 8284 |
| 10 | 42324 |
| 11 | 231950 |
| 12 | 1357264 |
| 13 | 8427194 |
| 14 | 55289280 |
| 15 | 381798704 |
| 16 | 2765918869 |
| 17 | 20960284294 |
| 18 | 165729748096 |
| 19 | 1364153612318 |
| 20 | 11665484452558 |
| 21 | 103448316471556 |
| 22 | 949739632545452 |
| 23 | 9013431476894646 |
[1,2,4,11,30,108,406,1764,8284,42324,231950, 1357264,8427194,55289280,381798704,2765918869, 20960284294,165729748096,1364153612318, 11665484452558,103448316471556,949739632545452, 9013431476894646] |