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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 22 |
| 4 | 117 |
| 5 | 654 |
| 6 | 3843 |
| 7 | 23323 |
| 8 | 145172 |
| 9 | 921508 |
| 10 | 5942737 |
| 11 | 38825546 |
| 12 | 256431172 |
| 13 | 1709356836 |
| 14 | 11485249995 |
| 15 | 77703736926 |
| 16 | 528893901963 |
| 17 | 3619228605738 |
| 18 | 24884558358426 |
| 19 | 171828674445330 |
| 20 | 1191050708958096 |
| 21 | 8284698825305832 |
[1,1,5,22,117,654,3843,23323,145172,921508, 5942737,38825546,256431172,1709356836,11485249995, 77703736926,528893901963,3619228605738, 24884558358426,171828674445330,1191050708958096, 8284698825305832] |