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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 218 |
| 3 | 22815 |
| 4 | 703760 |
| 5 | 10194250 |
| 6 | 90775566 |
| 7 | 576941778 |
| 8 | 2863870080 |
| 9 | 11769161895 |
| 10 | 41669295250 |
| 11 | 130772947481 |
| 12 | 371513523888 |
| 13 | 970769847320 |
| 14 | 2362273657030 |
| 15 | 5406141568500 |
| 16 | 11728193258496 |
| 17 | 24276032182173 |
| 18 | 48201464902410 |
| 19 | 92221684354915 |
[0,1,218,22815,703760,10194250,90775566,576941778, 2863870080,11769161895,41669295250,130772947481, 371513523888,970769847320,2362273657030, 5406141568500,11728193258496,24276032182173, 48201464902410,92221684354915] |