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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 28 |
| 3 | 292 |
| 4 | 4060 |
| 5 | 70564 |
| 6 | 1471708 |
| 7 | 35810212 |
| 8 | 995827420 |
| 9 | 31153998244 |
| 10 | 1082931514588 |
| 11 | 41407678132132 |
| 12 | 1727226633730780 |
| 13 | 78051253062575524 |
| 14 | 3798351192214837468 |
| 15 | 198049421007186054052 |
| 16 | 11014905131587945490140 |
| 17 | 650903915009792820650404 |
| 18 | 40726453234725158535472348 |
[1,4,28,292,4060,70564,1471708,35810212,995827420, 31153998244,1082931514588,41407678132132, 1727226633730780,78051253062575524, 3798351192214837468,198049421007186054052, 11014905131587945490140,650903915009792820650404, 40726453234725158535472348] |