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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 39 |
| 5 | 112 |
| 6 | 512 |
| 7 | 1660 |
| 8 | 7796 |
| 9 | 27224 |
| 10 | 129917 |
| 11 | 477245 |
| 12 | 2301281 |
| 13 | 8769055 |
| 14 | 42591564 |
| 15 | 166860618 |
| 16 | 814734888 |
| 17 | 3262097542 |
| 18 | 15991318693 |
| 19 | 65159871299 |
| 20 | 320406115972 |
| 21 | 1324542450930 |
| 22 | 6528900687902 |
| 23 | 27318534528929 |
| 24 | 134920901848093 |
| 25 | 570376728242050 |
| 26 | 2821473268289106 |
| 27 | 12033776552315483 |
| 28 | 59605851930799209 |
[1,1,4,9,39,112,512,1660,7796,27224,129917,477245, 2301281,8769055,42591564,166860618,814734888, 3262097542,15991318693,65159871299,320406115972, 1324542450930,6528900687902,27318534528929, 134920901848093,570376728242050,2821473268289106, 12033776552315483,59605851930799209] |