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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 41 |
| 5 | 244 |
| 6 | 1605 |
| 7 | 11350 |
| 8 | 84949 |
| 9 | 666221 |
| 10 | 5439193 |
| 11 | 46026398 |
| 12 | 402493943 |
| 13 | 3630344538 |
| 14 | 33731558974 |
| 15 | 322633261521 |
| 16 | 3175444787672 |
| 17 | 32156075992687 |
| 18 | 335029146470043 |
| 19 | 3591545445240954 |
| 20 | 39615629451300230 |
| 21 | 449583342724740800 |
[1,1,2,8,41,244,1605,11350,84949,666221,5439193, 46026398,402493943,3630344538,33731558974, 322633261521,3175444787672,32156075992687, 335029146470043,3591545445240954, 39615629451300230,449583342724740800] |