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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 24 |
| 2 | 312 |
| 3 | 2912 |
| 4 | 21816 |
| 5 | 139152 |
| 6 | 783328 |
| 7 | 3986112 |
| 8 | 18650424 |
| 9 | 81251896 |
| 10 | 332798544 |
| 11 | 1291339296 |
| 12 | 4776117216 |
| 13 | 16922753616 |
| 14 | 57683178432 |
| 15 | 189821722688 |
| 16 | 604884735288 |
| 17 | 1871370360240 |
| 18 | 5633654421720 |
| 19 | 16535803556064 |
| 20 | 47405095227984 |
| 21 | 132942579098368 |
| 22 | 365211946954656 |
[1,24,312,2912,21816,139152,783328,3986112, 18650424,81251896,332798544,1291339296,4776117216, 16922753616,57683178432,189821722688,604884735288, 1871370360240,5633654421720,16535803556064, 47405095227984,132942579098368,365211946954656] |