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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 240 |
| 3 | 6480 |
| 4 | 65280 |
| 5 | 390000 |
| 6 | 1678320 |
| 7 | 5762400 |
| 8 | 16773120 |
| 9 | 43040160 |
| 10 | 99990000 |
| 11 | 214344240 |
| 12 | 429960960 |
| 13 | 815702160 |
| 14 | 1475750640 |
| 15 | 2562840000 |
| 16 | 4294901760 |
| 17 | 6975673920 |
| 18 | 11019855600 |
| 19 | 16983432720 |
| 20 | 25599840000 |
| 21 | 37822664880 |
| 22 | 54875639280 |
| 23 | 78310705440 |
| 24 | 110074982400 |
[0,0,240,6480,65280,390000,1678320,5762400, 16773120,43040160,99990000,214344240,429960960, 815702160,1475750640,2562840000,4294901760, 6975673920,11019855600,16983432720,25599840000, 37822664880,54875639280,78310705440,110074982400] |