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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 27 |
| 4 | 134 |
| 5 | 709 |
| 6 | 3892 |
| 7 | 22004 |
| 8 | 127250 |
| 9 | 749230 |
| 10 | 4476386 |
| 11 | 27071344 |
| 12 | 165398868 |
| 13 | 1019405720 |
| 14 | 6330482488 |
| 15 | 39571612357 |
| 16 | 248796862550 |
| 17 | 1572300095758 |
| 18 | 9981970108384 |
| 19 | 63633339713190 |
| 20 | 407162295120570 |
| 21 | 2614059813642256 |
| 22 | 16834457481559076 |
[1,1,6,27,134,709,3892,22004,127250,749230, 4476386,27071344,165398868,1019405720,6330482488, 39571612357,248796862550,1572300095758, 9981970108384,63633339713190,407162295120570, 2614059813642256,16834457481559076] |