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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 60 |
| 3 | 1624 |
| 4 | 66240 |
| 5 | 3711200 |
| 6 | 269670208 |
| 7 | 24435113216 |
| 8 | 2682916389632 |
| 9 | 349223324753408 |
| 10 | 52965538033020928 |
| 11 | 9229753832340117504 |
| 12 | 1826647528631522463744 |
| 13 | 406579171521484851396608 |
| 14 | 100934277604965329345822720 |
| 15 | 27746271707522968205726416896 |
[1,4,60,1624,66240,3711200,269670208,24435113216, 2682916389632,349223324753408,52965538033020928, 9229753832340117504,1826647528631522463744, 406579171521484851396608, 100934277604965329345822720, 27746271707522968205726416896] |