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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 3 |
| 5 | 12 |
| 6 | 3 |
| 7 | 126 |
| 8 | 153 |
| 9 | 765 |
| 10 | 1050 |
| 11 | 5348 |
| 12 | 14850 |
| 13 | 85050 |
| 14 | 501200 |
| 15 | 91280 |
| 16 | 3661983 |
| 17 | 25633881 |
| 18 | 66271296 |
| 19 | 215467945 |
| 20 | 254861640 |
| 21 | 5311480020 |
| 22 | 75327142968 |
| 23 | 122703152000 |
| 24 | 2187956957004 |
| 25 | 3449084839200 |
| 26 | 19305922856220 |
| 27 | 11327171375520 |
| 28 | 58038845751810 |
| 29 | 2222926571960640 |
[0,2,6,3,12,3,126,153,765,1050,5348,14850,85050, 501200,91280,3661983,25633881,66271296,215467945, 254861640,5311480020,75327142968,122703152000, 2187956957004,3449084839200,19305922856220, 11327171375520,58038845751810,2222926571960640] |