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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 12 |
| 5 | 33 |
| 6 | 90 |
| 7 | 246 |
| 8 | 672 |
| 9 | 1836 |
| 10 | 5016 |
| 11 | 13704 |
| 12 | 37440 |
| 13 | 102288 |
| 14 | 279456 |
| 15 | 763488 |
| 16 | 2085888 |
| 17 | 5698752 |
| 18 | 15569280 |
| 19 | 42536064 |
| 20 | 116210688 |
| 21 | 317493504 |
| 22 | 867408384 |
| 23 | 2369803776 |
| 24 | 6474424320 |
| 25 | 17688456192 |
| 26 | 48325761024 |
| 27 | 132028434432 |
| 28 | 360708390912 |
[1,2,5,12,33,90,246,672,1836,5016,13704,37440, 102288,279456,763488,2085888,5698752,15569280, 42536064,116210688,317493504,867408384,2369803776, 6474424320,17688456192,48325761024,132028434432, 360708390912] |