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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 33 |
| 4 | 384 |
| 5 | 5945 |
| 6 | 115680 |
| 7 | 2713417 |
| 8 | 74568704 |
| 9 | 2350925649 |
| 10 | 83660474880 |
| 11 | 3317599815761 |
| 12 | 145087264278528 |
| 13 | 6937450761100873 |
| 14 | 360078818344534016 |
| 15 | 20162761727269502265 |
| 16 | 1211588127198611374080 |
| 17 | 77769423447774393465377 |
| 18 | 5310706204624302598127616 |
| 19 | 384439720034220718046773249 |
[1,1,4,33,384,5945,115680,2713417,74568704, 2350925649,83660474880,3317599815761, 145087264278528,6937450761100873, 360078818344534016,20162761727269502265, 1211588127198611374080,77769423447774393465377, 5310706204624302598127616, 384439720034220718046773249] |