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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 6 |
| 5 | 15 |
| 6 | 36 |
| 7 | 81 |
| 8 | 180 |
| 9 | 405 |
| 10 | 918 |
| 11 | 2079 |
| 12 | 4698 |
| 13 | 10611 |
| 14 | 23976 |
| 15 | 54189 |
| 16 | 122472 |
| 17 | 276777 |
| 18 | 625482 |
| 19 | 1413531 |
| 20 | 3194478 |
| 21 | 7219287 |
| 22 | 16315020 |
| 23 | 36870633 |
| 24 | 83324700 |
| 25 | 188307261 |
| 26 | 425559582 |
| 27 | 961731063 |
| 28 | 2173436226 |
| 29 | 4911794235 |
| 30 | 11100267216 |
| 31 | 25085727621 |
[0,1,2,3,6,15,36,81,180,405,918,2079,4698,10611, 23976,54189,122472,276777,625482,1413531,3194478, 7219287,16315020,36870633,83324700,188307261, 425559582,961731063,2173436226,4911794235, 11100267216,25085727621] |