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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 28 |
| 2 | 134 |
| 3 | 650 |
| 4 | 3168 |
| 5 | 15486 |
| 6 | 75848 |
| 7 | 372024 |
| 8 | 1826730 |
| 9 | 8977530 |
| 10 | 44151860 |
| 11 | 217269760 |
| 12 | 1069715430 |
| 13 | 5268960200 |
| 14 | 25962370558 |
| 15 | 127969407686 |
| 16 | 630947807506 |
| 17 | 3111658441818 |
| 18 | 15349331786976 |
| 19 | 75731342285276 |
| 20 | 373715745367376 |
[1,28,134,650,3168,15486,75848,372024,1826730, 8977530,44151860,217269760,1069715430,5268960200, 25962370558,127969407686,630947807506, 3111658441818,15349331786976,75731342285276, 373715745367376] |