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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 140 |
| 3 | 28 |
| 4 | 20020 |
| 5 | 4004 |
| 6 | 6466460 |
| 7 | 184756 |
| 8 | 148728580 |
| 9 | 29745716 |
| 10 | 133706993420 |
| 11 | 2431036244 |
| 12 | 449741705140 |
| 13 | 31885268 |
| 14 | 670910837521540 |
| 15 | 134182167504308 |
| 16 | 409926521725660940 |
| 17 | 4822664961478364 |
| 18 | 1278006214791766460 |
| 19 | 1921813856829724 |
| 20 | 242081282475556183660 |
| 21 | 4401477863191930612 |
[1,4,140,28,20020,4004,6466460,184756,148728580, 29745716,133706993420,2431036244,449741705140, 31885268,670910837521540,134182167504308, 409926521725660940,4822664961478364, 1278006214791766460,1921813856829724, 242081282475556183660,4401477863191930612] |