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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 144 |
| 3 | 1068 |
| 4 | 9936 |
| 5 | 55500 |
| 6 | 640992 |
| 7 | 3562968 |
| 8 | 31412208 |
| 9 | 220709400 |
| 10 | 227429400 |
| 11 | 228238488 |
| 12 | 1922263344 |
| 13 | 11150046252 |
| 14 | 11432420652 |
| 15 | 75796404672 |
| 16 | 94197649008 |
| 17 | 96503566608 |
| 18 | 419850417612 |
| 19 | 546394287000 |
| 20 | 3939440152944 |
| 21 | 4615731883344 |
[0,144,1068,9936,55500,640992,3562968,31412208, 220709400,227429400,228238488,1922263344, 11150046252,11432420652,75796404672,94197649008, 96503566608,419850417612,546394287000, 3939440152944,4615731883344] |