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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 51 |
| 4 | 371 |
| 5 | 2699 |
| 6 | 19635 |
| 7 | 142843 |
| 8 | 1039171 |
| 9 | 7559883 |
| 10 | 54997523 |
| 11 | 400102427 |
| 12 | 2910712035 |
| 13 | 21175189099 |
| 14 | 154047747763 |
| 15 | 1120684612539 |
| 16 | 8152887783299 |
| 17 | 59311583708171 |
| 18 | 431486861523795 |
| 19 | 3139031198082907 |
| 20 | 22836192109627939 |
[0,1,7,51,371,2699,19635,142843,1039171,7559883, 54997523,400102427,2910712035,21175189099, 154047747763,1120684612539,8152887783299, 59311583708171,431486861523795,3139031198082907, 22836192109627939] |