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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 20 |
| 4 | 72 |
| 5 | 256 |
| 6 | 912 |
| 7 | 3248 |
| 8 | 11568 |
| 9 | 41200 |
| 10 | 146736 |
| 11 | 522608 |
| 12 | 1861296 |
| 13 | 6629104 |
| 14 | 23609904 |
| 15 | 84087920 |
| 16 | 299483568 |
| 17 | 1066626544 |
| 18 | 3798846768 |
| 19 | 13529793392 |
| 20 | 48187073712 |
| 21 | 171620807920 |
| 22 | 611236571184 |
| 23 | 2176951329392 |
| 24 | 7753327130544 |
[1,6,20,72,256,912,3248,11568,41200,146736,522608, 1861296,6629104,23609904,84087920,299483568, 1066626544,3798846768,13529793392,48187073712, 171620807920,611236571184,2176951329392, 7753327130544] |