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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 26 |
| 4 | 139 |
| 5 | 765 |
| 6 | 6221 |
| 7 | 46898 |
| 8 | 292690 |
| 9 | 1722770 |
| 10 | 10915890 |
| 11 | 73213113 |
| 12 | 480069015 |
| 13 | 3032127834 |
| 14 | 19084607287 |
| 15 | 122424984026 |
| 16 | 792495253960 |
| 17 | 5097255978957 |
| 18 | 32562226190102 |
| 19 | 208268070296589 |
| 20 | 1338186393004984 |
| 21 | 8611472163134863 |
[1,3,26,139,765,6221,46898,292690,1722770, 10915890,73213113,480069015,3032127834, 19084607287,122424984026,792495253960, 5097255978957,32562226190102,208268070296589, 1338186393004984,8611472163134863] |