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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 694 |
| 7 | 4581 |
| 8 | 33283 |
| 9 | 260805 |
| 10 | 2171393 |
| 11 | 18994464 |
| 12 | 173094540 |
| 13 | 1632480259 |
| 14 | 15851668551 |
| 15 | 157824649955 |
| 16 | 1605839173312 |
| 17 | 16652321922596 |
| 18 | 175596537163347 |
| 19 | 1879357191026029 |
| 20 | 20382942631855557 |
| 21 | 223719376672365073 |
| 22 | 2482094083780961295 |
| 23 | 27808544385768051233 |
[1,1,2,6,24,119,694,4581,33283,260805,2171393, 18994464,173094540,1632480259,15851668551, 157824649955,1605839173312,16652321922596, 175596537163347,1879357191026029, 20382942631855557,223719376672365073, 2482094083780961295,27808544385768051233] |