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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 18 |
| 4 | 133 |
| 5 | 873 |
| 6 | 5182 |
| 7 | 27786 |
| 8 | 135370 |
| 9 | 602454 |
| 10 | 2466628 |
| 11 | 9358497 |
| 12 | 33134431 |
| 13 | 110184932 |
| 14 | 346141949 |
| 15 | 1032550097 |
| 16 | 2938104492 |
| 17 | 8006865684 |
| 18 | 20971632456 |
| 19 | 52958252851 |
| 20 | 129291697111 |
| 21 | 305924724070 |
| 22 | 703108665327 |
| 23 | 1572722761341 |
[2,18,133,873,5182,27786,135370,602454,2466628, 9358497,33134431,110184932,346141949,1032550097, 2938104492,8006865684,20971632456,52958252851, 129291697111,305924724070,703108665327, 1572722761341] |