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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 22 |
| 5 | 141 |
| 6 | 988 |
| 7 | 7337 |
| 8 | 56749 |
| 9 | 452332 |
| 10 | 3689697 |
| 11 | 30652931 |
| 12 | 258465558 |
| 13 | 2206330790 |
| 14 | 19029531220 |
| 15 | 165582392070 |
| 16 | 1451789520435 |
| 17 | 12813638048184 |
| 18 | 113755675163767 |
| 19 | 1015119850103821 |
| 20 | 9100463691522759 |
| 21 | 81923222827031025 |
[1,4,22,141,988,7337,56749,452332,3689697, 30652931,258465558,2206330790,19029531220, 165582392070,1451789520435,12813638048184, 113755675163767,1015119850103821,9100463691522759, 81923222827031025] |