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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 75 |
| 6 | 262 |
| 7 | 891 |
| 8 | 2964 |
| 9 | 9700 |
| 10 | 31374 |
| 11 | 100639 |
| 12 | 320949 |
| 13 | 1019396 |
| 14 | 3228687 |
| 15 | 10206180 |
| 16 | 32219494 |
| 17 | 101619194 |
| 18 | 320303001 |
| 19 | 1009163739 |
| 20 | 3178610330 |
| 21 | 10009874543 |
| 22 | 31518335944 |
| 23 | 99233864812 |
| 24 | 312414443206 |
| 25 | 983524845979 |
[1,2,6,21,75,262,891,2964,9700,31374,100639, 320949,1019396,3228687,10206180,32219494, 101619194,320303001,1009163739,3178610330, 10009874543,31518335944,99233864812,312414443206, 983524845979] |