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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 64 |
| 3 | 192 |
| 4 | 840 |
| 5 | 3246 |
| 6 | 12818 |
| 7 | 51240 |
| 8 | 203104 |
| 9 | 809436 |
| 10 | 3222418 |
| 11 | 12842530 |
| 12 | 51200418 |
| 13 | 204173560 |
| 14 | 814433476 |
| 15 | 3249025434 |
| 16 | 12962845362 |
| 17 | 51721055986 |
| 18 | 206371682824 |
| 19 | 823458800224 |
| 20 | 3285784448274 |
| 21 | 13111130921510 |
| 22 | 52317080184316 |
[18,64,192,840,3246,12818,51240,203104,809436, 3222418,12842530,51200418,204173560,814433476, 3249025434,12962845362,51721055986,206371682824, 823458800224,3285784448274,13111130921510, 52317080184316] |