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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 60 |
| 5 | 288 |
| 6 | 1384 |
| 7 | 6628 |
| 8 | 31772 |
| 9 | 152304 |
| 10 | 730036 |
| 11 | 3499340 |
| 12 | 16773680 |
| 13 | 80402532 |
| 14 | 385399644 |
| 15 | 1847365808 |
| 16 | 8855120468 |
| 17 | 42445929772 |
| 18 | 203459338800 |
| 19 | 975257291396 |
| 20 | 4674775757500 |
| 21 | 22407962058928 |
| 22 | 107409807372276 |
| 23 | 514855687878924 |
[1,3,13,60,288,1384,6628,31772,152304,730036, 3499340,16773680,80402532,385399644,1847365808, 8855120468,42445929772,203459338800,975257291396, 4674775757500,22407962058928,107409807372276, 514855687878924] |