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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 63 |
| 4 | 668 |
| 5 | 7850 |
| 6 | 115914 |
| 7 | 1847286 |
| 8 | 34031024 |
| 9 | 682177464 |
| 10 | 15049816200 |
| 11 | 357564279600 |
| 12 | 9212847784392 |
| 13 | 252552128708568 |
| 14 | 7395084613746816 |
| 15 | 229412209982127480 |
| 16 | 7524339637608261120 |
| 17 | 259675490280634374720 |
| 18 | 9418707076419411194304 |
| 19 | 357606237255136232451264 |
[1,1,8,63,668,7850,115914,1847286,34031024, 682177464,15049816200,357564279600,9212847784392, 252552128708568,7395084613746816, 229412209982127480,7524339637608261120, 259675490280634374720,9418707076419411194304, 357606237255136232451264] |