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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 160 |
| 5 | 1408 |
| 6 | 13760 |
| 7 | 140288 |
| 8 | 1459200 |
| 9 | 15595520 |
| 10 | 168584192 |
| 11 | 1847791616 |
| 12 | 20524785664 |
| 13 | 230327189504 |
| 14 | 2605161103360 |
| 15 | 29668221648896 |
| 16 | 340391560216576 |
| 17 | 3932276970749952 |
| 18 | 45577849469665280 |
| 19 | 529120083810713600 |
| 20 | 6194461391984787456 |
| 21 | 73492658811551350784 |
| 22 | 862792881224493826048 |
| 23 | 9756093957689676136448 |
| 24 | 117188194561127830519808 |
| 25 | 1695314645779792548331520 |
[1,4,16,160,1408,13760,140288,1459200,15595520, 168584192,1847791616,20524785664,230327189504, 2605161103360,29668221648896,340391560216576, 3932276970749952,45577849469665280, 529120083810713600,6194461391984787456, 73492658811551350784,862792881224493826048, 9756093957689676136448,117188194561127830519808, 1695314645779792548331520] |