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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 45 |
| 6 | 120 |
| 7 | 336 |
| 8 | 920 |
| 9 | 2574 |
| 10 | 7190 |
| 11 | 20262 |
| 12 | 57192 |
| 13 | 162318 |
| 14 | 461622 |
| 15 | 1317165 |
| 16 | 3766096 |
| 17 | 10792399 |
| 18 | 30980862 |
| 19 | 89084844 |
| 20 | 256524560 |
| 21 | 739658472 |
| 22 | 2135213982 |
| 23 | 6170505665 |
| 24 | 17849399616 |
| 25 | 51679366125 |
| 26 | 149750549260 |
| 27 | 434260826883 |
| 28 | 1260197855532 |
| 29 | 3659410074932 |
[1,2,6,16,45,120,336,920,2574,7190,20262,57192, 162318,461622,1317165,3766096,10792399,30980862, 89084844,256524560,739658472,2135213982, 6170505665,17849399616,51679366125,149750549260, 434260826883,1260197855532,3659410074932] |