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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 15 |
| 5 | 41 |
| 6 | 113 |
| 7 | 327 |
| 8 | 982 |
| 9 | 3066 |
| 10 | 9892 |
| 11 | 32820 |
| 12 | 111390 |
| 13 | 385042 |
| 14 | 1350722 |
| 15 | 4795246 |
| 16 | 17191535 |
| 17 | 62139697 |
| 18 | 226167557 |
| 19 | 828085651 |
| 20 | 3047683955 |
| 21 | 11267975677 |
| 22 | 41829610607 |
| 23 | 155848125601 |
| 24 | 582566960465 |
| 25 | 2184167358991 |
| 26 | 8211247681373 |
[0,1,2,6,15,41,113,327,982,3066,9892,32820,111390, 385042,1350722,4795246,17191535,62139697, 226167557,828085651,3047683955,11267975677, 41829610607,155848125601,582566960465, 2184167358991,8211247681373] |