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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 56 |
| 4 | 1024 |
| 5 | 21212 |
| 6 | 473056 |
| 7 | 11074656 |
| 8 | 268419072 |
| 9 | 6677240840 |
| 10 | 169503014016 |
| 11 | 4373238900672 |
| 12 | 114340618960896 |
| 13 | 3022828138341280 |
| 14 | 80668863489274880 |
| 15 | 2170196738706696448 |
| 16 | 58793507835449704448 |
| 17 | 1602579845950784683616 |
| 18 | 43919681465696136388608 |
| 19 | 1209451899880085285430528 |
[1,4,56,1024,21212,473056,11074656,268419072, 6677240840,169503014016,4373238900672, 114340618960896,3022828138341280, 80668863489274880,2170196738706696448, 58793507835449704448,1602579845950784683616, 43919681465696136388608,1209451899880085285430528] |