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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 42 |
| 4 | 1168 |
| 5 | 84180 |
| 6 | 15107328 |
| 7 | 6495857312 |
| 8 | 6492989426432 |
| 9 | 14753072834027424 |
| 10 | 74941835564789489280 |
| 11 | 840421638561217307501632 |
| 12 | 20603672787268830442103493120 |
| 13 | 1095629510349075557617215030858112 |
| 14 | 125563465926494619940863277689861766144 |
[1,1,4,42,1168,84180,15107328,6495857312, 6492989426432,14753072834027424, 74941835564789489280,840421638561217307501632, 20603672787268830442103493120, 1095629510349075557617215030858112, 125563465926494619940863277689861766144] |