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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 20 |
| 4 | 320 |
| 5 | 460 |
| 6 | 5440 |
| 7 | 14260 |
| 8 | 12920 |
| 9 | 168640 |
| 10 | 103360 |
| 11 | 594320 |
| 12 | 3878720 |
| 13 | 2377280 |
| 14 | 9211960 |
| 15 | 18423920 |
| 16 | 36847840 |
| 17 | 125995840 |
| 18 | 73695680 |
| 19 | 865924240 |
| 20 | 976467760 |
| 21 | 1952935520 |
| 22 | 3463696960 |
| 23 | 3905871040 |
| 24 | 31246968320 |
| 25 | 22946992360 |
[1,4,20,320,460,5440,14260,12920,168640,103360, 594320,3878720,2377280,9211960,18423920,36847840, 125995840,73695680,865924240,976467760,1952935520, 3463696960,3905871040,31246968320,22946992360] |