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| n | a(n) |
|---|---|
| 0 | 18 |
| 1 | 150 |
| 2 | 820 |
| 3 | 3726 |
| 4 | 15492 |
| 5 | 61660 |
| 6 | 240328 |
| 7 | 928110 |
| 8 | 3572692 |
| 9 | 13749580 |
| 10 | 52977216 |
| 11 | 204478276 |
| 12 | 790747504 |
| 13 | 3063728856 |
| 14 | 11891504944 |
| 15 | 46231328174 |
| 16 | 180005765748 |
| 17 | 701823431740 |
| 18 | 2739725128448 |
| 19 | 10707198384348 |
| 20 | 41888225645152 |
| 21 | 164027934617024 |
[18,150,820,3726,15492,61660,240328,928110, 3572692,13749580,52977216,204478276,790747504, 3063728856,11891504944,46231328174,180005765748, 701823431740,2739725128448,10707198384348, 41888225645152,164027934617024] |