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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 12 |
| 5 | 60 |
| 6 | 270 |
| 7 | 1296 |
| 8 | 6048 |
| 9 | 29160 |
| 10 | 155520 |
| 11 | 883872 |
| 12 | 5038848 |
| 13 | 28304640 |
| 14 | 157697280 |
| 15 | 877515379 |
| 16 | 4899999744 |
| 17 | 27554100480 |
| 18 | 156116108160 |
| 19 | 889181991936 |
| 20 | 5078255822436 |
| 21 | 29045467518171 |
| 22 | 166348496793600 |
| 23 | 954240788994048 |
| 24 | 5484237660094464 |
| 25 | 31581437286776820 |
[0,0,1,12,60,270,1296,6048,29160,155520,883872, 5038848,28304640,157697280,877515379,4899999744, 27554100480,156116108160,889181991936, 5078255822436,29045467518171,166348496793600, 954240788994048,5484237660094464, 31581437286776820] |