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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 62 |
| 5 | 300 |
| 6 | 1635 |
| 7 | 9413 |
| 8 | 54505 |
| 9 | 321655 |
| 10 | 1938621 |
| 11 | 11834305 |
| 12 | 72975115 |
| 13 | 454385175 |
| 14 | 2852742151 |
| 15 | 18034439209 |
| 16 | 114709370133 |
| 17 | 733605250447 |
| 18 | 4714351916849 |
| 19 | 30426720332601 |
| 20 | 197141722168571 |
| 21 | 1281835943761551 |
[1,1,2,12,62,300,1635,9413,54505,321655,1938621, 11834305,72975115,454385175,2852742151, 18034439209,114709370133,733605250447, 4714351916849,30426720332601,197141722168571, 1281835943761551] |