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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 25 |
| 3 | 144 |
| 4 | 1024 |
| 5 | 7396 |
| 6 | 51076 |
| 7 | 345744 |
| 8 | 2547216 |
| 9 | 19114384 |
| 10 | 145564225 |
| 11 | 1111822336 |
| 12 | 8343726336 |
| 13 | 62292173056 |
| 14 | 459542986816 |
| 15 | 3371072258304 |
| 16 | 25398293867584 |
| 17 | 192578234089536 |
| 18 | 1474993183809600 |
| 19 | 11338593510740224 |
[1,4,25,144,1024,7396,51076,345744,2547216, 19114384,145564225,1111822336,8343726336, 62292173056,459542986816,3371072258304, 25398293867584,192578234089536,1474993183809600, 11338593510740224] |