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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 71 |
| 3 | 580 |
| 4 | 5104 |
| 5 | 48860 |
| 6 | 509004 |
| 7 | 5753736 |
| 8 | 70290936 |
| 9 | 924118272 |
| 10 | 13020978816 |
| 11 | 195869441664 |
| 12 | 3134328981120 |
| 13 | 53180752331520 |
| 14 | 953884282141440 |
| 15 | 18037635241029120 |
| 16 | 358689683932346880 |
| 17 | 7483713725055744000 |
| 18 | 163478034254755584000 |
| 19 | 3731670622213083648000 |
[1,9,71,580,5104,48860,509004,5753736,70290936, 924118272,13020978816,195869441664,3134328981120, 53180752331520,953884282141440,18037635241029120, 358689683932346880,7483713725055744000, 163478034254755584000,3731670622213083648000] |