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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 20 |
| 3 | 252 |
| 4 | 1296 |
| 5 | 4232 |
| 6 | 10668 |
| 7 | 22956 |
| 8 | 43832 |
| 9 | 77160 |
| 10 | 126972 |
| 11 | 198176 |
| 12 | 296976 |
| 13 | 429252 |
| 14 | 602876 |
| 15 | 825552 |
| 16 | 1106376 |
| 17 | 1454192 |
| 18 | 1879956 |
| 19 | 2397024 |
| 20 | 3014312 |
| 21 | 3747564 |
| 22 | 4609476 |
[0,20,252,1296,4232,10668,22956,43832,77160, 126972,198176,296976,429252,602876,825552,1106376, 1454192,1879956,2397024,3014312,3747564,4609476] |