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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 228 |
| 5 | 600 |
| 6 | 12357 |
| 7 | 68796 |
| 8 | 275888 |
| 9 | 872532 |
| 10 | 2344025 |
| 11 | 5580762 |
| 12 | 12107196 |
| 13 | 24392446 |
| 14 | 46261537 |
| 15 | 83426400 |
| 16 | 144157632 |
| 17 | 240119696 |
| 18 | 387393921 |
| 19 | 607715342 |
| 20 | 929951100 |
[0,0,0,228,600,12357,68796,275888,872532,2344025, 5580762,12107196,24392446,46261537,83426400, 144157632,240119696,387393921,607715342,929951100] |