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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 14 |
| 3 | 52 |
| 4 | 196 |
| 5 | 733 |
| 6 | 2744 |
| 7 | 10267 |
| 8 | 38416 |
| 9 | 143740 |
| 10 | 537824 |
| 11 | 2012353 |
| 12 | 7529536 |
| 13 | 28172944 |
| 14 | 105413504 |
| 15 | 394421216 |
| 16 | 1475789056 |
| 17 | 5521897023 |
| 18 | 20661046784 |
| 19 | 77306558318 |
| 20 | 289254654976 |
| 21 | 1082291816450 |
| 22 | 4049565169664 |
[1,4,14,52,196,733,2744,10267,38416,143740,537824, 2012353,7529536,28172944,105413504,394421216, 1475789056,5521897023,20661046784,77306558318, 289254654976,1082291816450,4049565169664] |