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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 32 |
| 3 | 228 |
| 4 | 1652 |
| 5 | 11980 |
| 6 | 86916 |
| 7 | 630604 |
| 8 | 4575332 |
| 9 | 33196332 |
| 10 | 240856196 |
| 11 | 1747533964 |
| 12 | 12679246500 |
| 13 | 91994373868 |
| 14 | 667465912772 |
| 15 | 4842804251724 |
| 16 | 35137004861924 |
| 17 | 254936818941100 |
| 18 | 1849696122577668 |
| 19 | 13420484966010892 |
| 20 | 97372435679847716 |
[4,32,228,1652,11980,86916,630604,4575332, 33196332,240856196,1747533964,12679246500, 91994373868,667465912772,4842804251724, 35137004861924,254936818941100,1849696122577668, 13420484966010892,97372435679847716] |