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| n | a(n) |
|---|---|
| 3 | 20 |
| 4 | 140 |
| 5 | 405 |
| 6 | 2856 |
| 7 | 25296 |
| 8 | 111720 |
| 9 | 25984 |
| 10 | 5474000 |
| 11 | 237600 |
| 12 | 223826688 |
| 13 | 3852800 |
| 14 | 268565760 |
| 15 | 1834725376 |
| 16 | 175861400000 |
| 17 | 335674368 |
| 18 | 2863363937280 |
| 19 | 4383831556096 |
| 20 | 206015846400 |
| 21 | 3400704000 |
| 22 | 938209120583680 |
| 23 | 2981338216980480 |
| 24 | 21463949229465600 |
| 25 | 45410367307776 |
| 26 | 72056803765911552 |
[20,140,405,2856,25296,111720,25984,5474000, 237600,223826688,3852800,268565760,1834725376, 175861400000,335674368,2863363937280, 4383831556096,206015846400,3400704000, 938209120583680,2981338216980480, 21463949229465600,45410367307776, 72056803765911552] |