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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 16 |
| 3 | 63 |
| 4 | 249 |
| 5 | 984 |
| 6 | 3888 |
| 7 | 15363 |
| 8 | 60705 |
| 9 | 239868 |
| 10 | 947808 |
| 11 | 3745143 |
| 12 | 14798457 |
| 13 | 58474224 |
| 14 | 231053472 |
| 15 | 912978459 |
| 16 | 3607518465 |
| 17 | 14254651188 |
| 18 | 56325444336 |
| 19 | 222562841967 |
| 20 | 879428812473 |
| 21 | 3474951296328 |
| 22 | 13730828852304 |
| 23 | 54255626883315 |
[4,16,63,249,984,3888,15363,60705,239868,947808, 3745143,14798457,58474224,231053472,912978459, 3607518465,14254651188,56325444336,222562841967, 879428812473,3474951296328,13730828852304, 54255626883315] |