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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 48 |
| 4 | 256 |
| 5 | 800 |
| 6 | 3840 |
| 7 | 12544 |
| 8 | 65536 |
| 9 | 186624 |
| 10 | 986880 |
| 11 | 3345408 |
| 12 | 16515072 |
| 13 | 52306176 |
| 14 | 252645120 |
| 15 | 760320000 |
| 16 | 4288266240 |
| 17 | 13628740608 |
| 18 | 64258375680 |
| 19 | 218462552064 |
| 20 | 1095233372160 |
| 21 | 3105655160832 |
| 22 | 16510446886912 |
| 23 | 56000724240384 |
| 24 | 280012271910912 |
| 25 | 869940000000000 |
[1,4,16,48,256,800,3840,12544,65536,186624,986880, 3345408,16515072,52306176,252645120,760320000, 4288266240,13628740608,64258375680,218462552064, 1095233372160,3105655160832,16510446886912, 56000724240384,280012271910912,869940000000000] |