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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 68 |
| 5 | 421 |
| 6 | 3015 |
| 7 | 24541 |
| 8 | 223884 |
| 9 | 2263381 |
| 10 | 25121075 |
| 11 | 303716281 |
| 12 | 3973432728 |
| 13 | 55931774473 |
| 14 | 842950049823 |
| 15 | 13543132571641 |
| 16 | 231076203767720 |
| 17 | 4172914800390601 |
| 18 | 79516457411189139 |
| 19 | 1594502063024173381 |
| 20 | 33564059780918830140 |
| 21 | 740003817243238436461 |
| 22 | 17053651856375402868743 |
[0,1,3,13,68,421,3015,24541,223884,2263381, 25121075,303716281,3973432728,55931774473, 842950049823,13543132571641,231076203767720, 4172914800390601,79516457411189139, 1594502063024173381,33564059780918830140, 740003817243238436461,17053651856375402868743] |