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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 25 |
| 6 | 83 |
| 7 | 282 |
| 8 | 971 |
| 9 | 3386 |
| 10 | 11940 |
| 11 | 42504 |
| 12 | 152546 |
| 13 | 551426 |
| 14 | 2005930 |
| 15 | 7337901 |
| 16 | 26976726 |
| 17 | 99618976 |
| 18 | 369349607 |
| 19 | 1374391706 |
| 20 | 5131186060 |
| 21 | 19214759396 |
| 22 | 72152791729 |
| 23 | 271629133830 |
| 24 | 1024989876797 |
| 25 | 3876208984221 |
| 26 | 14688301498888 |
| 27 | 55763768987236 |
| 28 | 212077310097784 |
[1,0,1,2,8,25,83,282,971,3386,11940,42504,152546, 551426,2005930,7337901,26976726,99618976, 369349607,1374391706,5131186060,19214759396, 72152791729,271629133830,1024989876797, 3876208984221,14688301498888,55763768987236, 212077310097784] |