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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 28 |
| 5 | 172 |
| 6 | 1269 |
| 7 | 10879 |
| 8 | 106343 |
| 9 | 1167970 |
| 10 | 14241792 |
| 11 | 190919195 |
| 12 | 2790920003 |
| 13 | 44184957237 |
| 14 | 753152722642 |
| 15 | 13752229833566 |
| 16 | 267809474619299 |
| 17 | 5540559819166056 |
| 18 | 121355678158129804 |
| 19 | 2805498395990301867 |
| 20 | 68265999939081386947 |
| 21 | 1744058001878302097109 |
[1,1,2,6,28,172,1269,10879,106343,1167970, 14241792,190919195,2790920003,44184957237, 753152722642,13752229833566,267809474619299, 5540559819166056,121355678158129804, 2805498395990301867,68265999939081386947, 1744058001878302097109] |