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| n | a(n) |
|---|---|
| -1 | 1 |
| 0 | 0 |
| 1 | 21 |
| 2 | 62 |
| 3 | 162 |
| 4 | 378 |
| 5 | 819 |
| 6 | 1680 |
| 7 | 3276 |
| 8 | 6138 |
| 9 | 11145 |
| 10 | 19662 |
| 11 | 33840 |
| 12 | 57048 |
| 13 | 94362 |
| 14 | 153432 |
| 15 | 245757 |
| 16 | 388218 |
| 17 | 605466 |
| 18 | 933414 |
| 19 | 1423614 |
| 20 | 2149586 |
| 21 | 3215844 |
| 22 | 4769544 |
| 23 | 7016572 |
| 24 | 10243896 |
| 25 | 14848809 |
| 26 | 21378276 |
| 27 | 30582360 |
| 28 | 43484304 |
| 29 | 61473438 |
| 30 | 86428896 |
[1,0,21,62,162,378,819,1680,3276,6138,11145,19662, 33840,57048,94362,153432,245757,388218,605466, 933414,1423614,2149586,3215844,4769544,7016572, 10243896,14848809,21378276,30582360,43484304, 61473438,86428896] |