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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 64 |
| 3 | 1792 |
| 4 | 70736 |
| 5 | 3600128 |
| 6 | 224255040 |
| 7 | 16521605376 |
| 8 | 1405131880000 |
| 9 | 135480346104896 |
| 10 | 14602769310474240 |
| 11 | 1739917222954854400 |
| 12 | 227081534040721917952 |
| 13 | 32217108743091290851328 |
| 14 | 4936803887495636263284736 |
| 15 | 812576030237749532251019264 |
| 16 | 142976863303365903802301729024 |
| 17 | 26781577193841845859144244087808 |
| 18 | 5320767287406003709062843236972544 |
| 19 | 1117525692987087894816123931091214336 |
[1,4,64,1792,70736,3600128,224255040,16521605376, 1405131880000,135480346104896,14602769310474240, 1739917222954854400,227081534040721917952, 32217108743091290851328,4936803887495636263284736, 812576030237749532251019264, 142976863303365903802301729024, 26781577193841845859144244087808, 5320767287406003709062843236972544, 1117525692987087894816123931091214336] |