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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 54 |
| 6 | 261 |
| 7 | 1344 |
| 8 | 7380 |
| 9 | 43099 |
| 10 | 265739 |
| 11 | 1717466 |
| 12 | 11586670 |
| 13 | 81422063 |
| 14 | 594828360 |
| 15 | 4508090145 |
| 16 | 35380563603 |
| 17 | 287130931064 |
| 18 | 2406309163514 |
| 19 | 20797551211656 |
| 20 | 185158224231178 |
| 21 | 1696132889163096 |
| 22 | 15969702544475270 |
[1,1,3,12,54,261,1344,7380,43099,265739,1717466, 11586670,81422063,594828360,4508090145, 35380563603,287130931064,2406309163514, 20797551211656,185158224231178,1696132889163096, 15969702544475270] |