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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 53 |
| 4 | 647 |
| 5 | 10092 |
| 6 | 191915 |
| 7 | 4309769 |
| 8 | 111682044 |
| 9 | 3281731611 |
| 10 | 107860953795 |
| 11 | 3921762633846 |
| 12 | 156322429050397 |
| 13 | 6779458454252941 |
| 14 | 317841794915501862 |
| 15 | 16020304439710056785 |
| 16 | 863955306007083830051 |
| 17 | 49641711131738762890764 |
| 18 | 3027776406780183894833791 |
| 19 | 195382900651186641677702197 |
[1,1,6,53,647,10092,191915,4309769,111682044, 3281731611,107860953795,3921762633846, 156322429050397,6779458454252941, 317841794915501862,16020304439710056785, 863955306007083830051,49641711131738762890764, 3027776406780183894833791, 195382900651186641677702197] |