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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 25 |
| 3 | 117 |
| 4 | 526 |
| 5 | 2397 |
| 6 | 10873 |
| 7 | 49398 |
| 8 | 224305 |
| 9 | 1018701 |
| 10 | 4626238 |
| 11 | 21009621 |
| 12 | 95412529 |
| 13 | 433304934 |
| 14 | 1967802505 |
| 15 | 8936542053 |
| 16 | 40584243694 |
| 17 | 184308525453 |
| 18 | 837015282217 |
| 19 | 3801205524822 |
| 20 | 17262723549985 |
| 21 | 78396609323709 |
[1,6,25,117,526,2397,10873,49398,224305,1018701, 4626238,21009621,95412529,433304934,1967802505, 8936542053,40584243694,184308525453,837015282217, 3801205524822,17262723549985,78396609323709] |