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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 70 |
| 5 | 805 |
| 6 | 12480 |
| 7 | 245847 |
| 8 | 5909338 |
| 9 | 168310515 |
| 10 | 5556486450 |
| 11 | 209003251240 |
| 12 | 8835266400450 |
| 13 | 415094928861530 |
| 14 | 21473740362658640 |
| 15 | 1213683089969940075 |
| 16 | 74446121738526773490 |
| 17 | 4927385997649620215895 |
| 18 | 350145746700442604768346 |
[1,1,2,9,70,805,12480,245847,5909338,168310515, 5556486450,209003251240,8835266400450, 415094928861530,21473740362658640, 1213683089969940075,74446121738526773490, 4927385997649620215895,350145746700442604768346] |