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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 36 |
| 6 | 199 |
| 7 | 1303 |
| 8 | 9844 |
| 9 | 84217 |
| 10 | 804738 |
| 11 | 8494461 |
| 12 | 98158214 |
| 13 | 1232430908 |
| 14 | 16706285647 |
| 15 | 243169268857 |
| 16 | 3782633071104 |
| 17 | 62623591954943 |
| 18 | 1099391947653438 |
| 19 | 20399828362013787 |
| 20 | 398929976857158503 |
[1,1,1,2,8,36,199,1303,9844,84217,804738,8494461, 98158214,1232430908,16706285647,243169268857, 3782633071104,62623591954943,1099391947653438, 20399828362013787,398929976857158503] |