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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 45 |
| 5 | 646 |
| 6 | 11791 |
| 7 | 256384 |
| 8 | 6423769 |
| 9 | 181427754 |
| 10 | 5689282946 |
| 11 | 195908618092 |
| 12 | 7345423236232 |
| 13 | 297860411541226 |
| 14 | 12990182010207113 |
| 15 | 606403416131651092 |
| 16 | 30175914326945883879 |
| 17 | 1594887978524453295830 |
| 18 | 89239745135865040868793 |
| 19 | 5270747814747645030300220 |
| 20 | 327731421167826049968117819 |
| 21 | 21401517667824383352272329174 |
[1,0,1,4,45,646,11791,256384,6423769,181427754, 5689282946,195908618092,7345423236232, 297860411541226,12990182010207113, 606403416131651092,30175914326945883879, 1594887978524453295830,89239745135865040868793, 5270747814747645030300220, 327731421167826049968117819, 21401517667824383352272329174] |