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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 63 |
| 5 | 398 |
| 6 | 2911 |
| 7 | 24177 |
| 8 | 224824 |
| 9 | 2313892 |
| 10 | 26107679 |
| 11 | 320412404 |
| 12 | 4249353369 |
| 13 | 60561549764 |
| 14 | 923107802463 |
| 15 | 14985538729504 |
| 16 | 258138422935578 |
| 17 | 4702896016961154 |
| 18 | 90350619640638353 |
| 19 | 1825564783445799571 |
| 20 | 38700814850328413380 |
| 21 | 858915876402686598209 |
| 22 | 19916917035087719607321 |
[1,1,3,12,63,398,2911,24177,224824,2313892, 26107679,320412404,4249353369,60561549764, 923107802463,14985538729504,258138422935578, 4702896016961154,90350619640638353, 1825564783445799571,38700814850328413380, 858915876402686598209,19916917035087719607321] |