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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 55 |
| 5 | 276 |
| 6 | 1477 |
| 7 | 8296 |
| 8 | 48393 |
| 9 | 291010 |
| 10 | 1794320 |
| 11 | 11297760 |
| 12 | 72413640 |
| 13 | 471309944 |
| 14 | 3108745785 |
| 15 | 20746732688 |
| 16 | 139899430981 |
| 17 | 952127880138 |
| 18 | 6533934575018 |
| 19 | 45175430719240 |
| 20 | 314467004704818 |
| 21 | 2202576030828096 |
| 22 | 15514620388706488 |
| 23 | 109851319423632192 |
| 24 | 781531332298053400 |
[1,1,3,12,55,276,1477,8296,48393,291010,1794320, 11297760,72413640,471309944,3108745785, 20746732688,139899430981,952127880138, 6533934575018,45175430719240,314467004704818, 2202576030828096,15514620388706488, 109851319423632192,781531332298053400] |