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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 16 |
| 3 | 96 |
| 4 | 512 |
| 5 | 2560 |
| 6 | 24576 |
| 7 | 229376 |
| 8 | 2097152 |
| 9 | 17956864 |
| 10 | 142606336 |
| 11 | 1107296256 |
| 12 | 8589934592 |
| 13 | 67612180480 |
| 14 | 541165879296 |
| 15 | 4363686772736 |
| 16 | 35184372088832 |
| 17 | 282583078273024 |
| 18 | 2260595906707456 |
| 19 | 18049582881570816 |
| 20 | 144115188075855872 |
| 21 | 1151793405676748800 |
[4,16,96,512,2560,24576,229376,2097152,17956864, 142606336,1107296256,8589934592,67612180480, 541165879296,4363686772736,35184372088832, 282583078273024,2260595906707456, 18049582881570816,144115188075855872, 1151793405676748800] |