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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 16 |
| 5 | 72 |
| 6 | 324 |
| 7 | 1728 |
| 8 | 9216 |
| 9 | 57600 |
| 10 | 360000 |
| 11 | 2592000 |
| 12 | 18662400 |
| 13 | 152409600 |
| 14 | 1244678400 |
| 15 | 11379916800 |
| 16 | 104044953600 |
| 17 | 1053455155200 |
| 18 | 10666233446400 |
| 19 | 118513704960000 |
| 20 | 1316818944000000 |
| 21 | 15933509222400000 |
| 22 | 192795461591040000 |
| 23 | 2523867860828160000 |
| 24 | 33039724723568640000 |
[0,1,4,16,72,324,1728,9216,57600,360000,2592000, 18662400,152409600,1244678400,11379916800, 104044953600,1053455155200,10666233446400, 118513704960000,1316818944000000, 15933509222400000,192795461591040000, 2523867860828160000,33039724723568640000] |