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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 21 |
| 4 | 98 |
| 5 | 575 |
| 6 | 3979 |
| 7 | 31304 |
| 8 | 277248 |
| 9 | 2739141 |
| 10 | 29898743 |
| 11 | 355083014 |
| 12 | 4584190984 |
| 13 | 63680965127 |
| 14 | 949202526375 |
| 15 | 15102175351080 |
| 16 | 255427113948896 |
| 17 | 4573909845546233 |
| 18 | 86542053988578763 |
| 19 | 1723504067599805402 |
| 20 | 36054646740337797072 |
| 21 | 790412592781303448523 |
[1,2,5,21,98,575,3979,31304,277248,2739141, 29898743,355083014,4584190984,63680965127, 949202526375,15102175351080,255427113948896, 4573909845546233,86542053988578763, 1723504067599805402,36054646740337797072, 790412592781303448523] |