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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 73 |
| 6 | 238 |
| 7 | 724 |
| 8 | 2075 |
| 9 | 5667 |
| 10 | 14892 |
| 11 | 37942 |
| 12 | 94273 |
| 13 | 229453 |
| 14 | 548954 |
| 15 | 1294440 |
| 16 | 3014775 |
| 17 | 6946951 |
| 18 | 15859864 |
| 19 | 35913898 |
| 20 | 80740541 |
| 21 | 180355281 |
| 22 | 400556262 |
| 23 | 884998396 |
| 24 | 1946157331 |
| 25 | 4261413163 |
| 26 | 9294577988 |
| 27 | 20199768414 |
| 28 | 43754979705 |
| 29 | 94489280917 |
| 30 | 203474076082 |
[1,2,6,21,73,238,724,2075,5667,14892,37942,94273, 229453,548954,1294440,3014775,6946951,15859864, 35913898,80740541,180355281,400556262,884998396, 1946157331,4261413163,9294577988,20199768414, 43754979705,94489280917,203474076082] |