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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 6 |
| 6 | 56 |
| 7 | 640 |
| 8 | 8256 |
| 9 | 115456 |
| 10 | 1710592 |
| 11 | 26468352 |
| 12 | 423641088 |
| 13 | 6966960128 |
| 14 | 117148778496 |
| 15 | 2006711795712 |
| 16 | 34918458982400 |
| 17 | 615857321410560 |
| 18 | 10989673088286720 |
| 19 | 198124551844921344 |
| 20 | 3604297438589878272 |
| 21 | 66099459892606664704 |
| 22 | 1220968511518137122816 |
| 23 | 22700172671958160244736 |
| 24 | 424526793381853406429184 |
[1,6,56,640,8256,115456,1710592,26468352, 423641088,6966960128,117148778496,2006711795712, 34918458982400,615857321410560,10989673088286720, 198124551844921344,3604297438589878272, 66099459892606664704,1220968511518137122816, 22700172671958160244736,424526793381853406429184] |