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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 32 |
| 3 | 160 |
| 4 | 1088 |
| 5 | 6016 |
| 6 | 38144 |
| 7 | 220672 |
| 8 | 1356800 |
| 9 | 8009728 |
| 10 | 48582656 |
| 11 | 289398784 |
| 12 | 1744781312 |
| 13 | 10435133440 |
| 14 | 62745018368 |
| 15 | 375933239296 |
| 16 | 2257746919424 |
| 17 | 13537891581952 |
| 18 | 81261709230080 |
| 19 | 487432816427008 |
| 20 | 2925146654375936 |
[1,4,32,160,1088,6016,38144,220672,1356800, 8009728,48582656,289398784,1744781312,10435133440, 62745018368,375933239296,2257746919424, 13537891581952,81261709230080,487432816427008, 2925146654375936] |