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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 12 |
| 3 | 40 |
| 4 | 144 |
| 5 | 544 |
| 6 | 2112 |
| 7 | 8320 |
| 8 | 33024 |
| 9 | 131584 |
| 10 | 525312 |
| 11 | 2099200 |
| 12 | 8392704 |
| 13 | 33562624 |
| 14 | 134234112 |
| 15 | 536903680 |
| 16 | 2147549184 |
| 17 | 8590065664 |
| 18 | 34360000512 |
| 19 | 137439477760 |
| 20 | 549756862464 |
| 21 | 2199025352704 |
| 22 | 8796097216512 |
| 23 | 35184380477440 |
| 24 | 140737505132544 |
| 25 | 562949986975744 |
[4,12,40,144,544,2112,8320,33024,131584,525312, 2099200,8392704,33562624,134234112,536903680, 2147549184,8590065664,34360000512,137439477760, 549756862464,2199025352704,8796097216512, 35184380477440,140737505132544,562949986975744] |