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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 7 |
| 7 | 142 |
| 8 | 1236 |
| 9 | 19389 |
| 10 | 197961 |
| 11 | 3119296 |
| 12 | 37007330 |
| 13 | 625269351 |
| 14 | 8518503575 |
| 15 | 156989400170 |
| 16 | 2424846690232 |
| 17 | 48850794161897 |
| 18 | 845427958969045 |
[0,0,0,0,1,7,142,1236,19389,197961,3119296, 37007330,625269351,8518503575,156989400170, 2424846690232,48850794161897,845427958969045] |