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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 7 |
| 6 | 33 |
| 7 | 200 |
| 8 | 1436 |
| 9 | 11742 |
| 10 | 107810 |
| 11 | 1097701 |
| 12 | 12274283 |
| 13 | 149523080 |
| 14 | 1970986053 |
| 15 | 27952165839 |
| 16 | 424364699555 |
| 17 | 6866992410975 |
| 18 | 117987415061287 |
| 19 | 2145225728387030 |
| 20 | 41149329880878478 |
| 21 | 830468293959547465 |
[1,1,1,1,2,7,33,200,1436,11742,107810,1097701, 12274283,149523080,1970986053,27952165839, 424364699555,6866992410975,117987415061287, 2145225728387030,41149329880878478, 830468293959547465] |