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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 616 |
| 4 | 12856 |
| 5 | 338728 |
| 6 | 10781176 |
| 7 | 402250216 |
| 8 | 17213590840 |
| 9 | 831013114792 |
| 10 | 44675458306168 |
| 11 | 2646758624166760 |
| 12 | 171319908334752184 |
| 13 | 12028779733435667752 |
| 14 | 910538645035885918456 |
| 15 | 73918475291961325824232 |
| 16 | 6406179168820339231897144 |
[1,4,40,616,12856,338728,10781176,402250216, 17213590840,831013114792,44675458306168, 2646758624166760,171319908334752184, 12028779733435667752,910538645035885918456, 73918475291961325824232,6406179168820339231897144] |