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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 8 |
| 3 | 22 |
| 4 | 66 |
| 5 | 222 |
| 6 | 862 |
| 7 | 3838 |
| 8 | 19542 |
| 9 | 111894 |
| 10 | 712282 |
| 11 | 4987672 |
| 12 | 38102844 |
| 13 | 315339898 |
| 14 | 2810523166 |
| 15 | 26838510154 |
| 16 | 273374835624 |
| 17 | 2958608945772 |
| 18 | 33903161435148 |
| 19 | 410085034127000 |
| 20 | 5221364826476796 |
| 21 | 69804505809732988 |
[1,3,8,22,66,222,862,3838,19542,111894,712282, 4987672,38102844,315339898,2810523166,26838510154, 273374835624,2958608945772,33903161435148, 410085034127000,5221364826476796, 69804505809732988] |