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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 7 |
| 3 | 18 |
| 4 | 98 |
| 5 | 210 |
| 6 | 969 |
| 7 | 1938 |
| 8 | 7037 |
| 9 | 15258 |
| 10 | 44815 |
| 11 | 93180 |
| 12 | 262391 |
| 13 | 518550 |
| 14 | 1311015 |
| 15 | 2657328 |
| 16 | 6189160 |
| 17 | 12124098 |
| 18 | 27239760 |
| 19 | 52063668 |
| 20 | 111630480 |
| 21 | 211503288 |
| 22 | 432900236 |
| 23 | 806091180 |
| 24 | 1610854427 |
| 25 | 2940167268 |
| 26 | 5691072911 |
| 27 | 10289144976 |
| 28 | 19402974147 |
| 29 | 34523231688 |
[1,0,7,18,98,210,969,1938,7037,15258,44815,93180, 262391,518550,1311015,2657328,6189160,12124098, 27239760,52063668,111630480,211503288,432900236, 806091180,1610854427,2940167268,5691072911, 10289144976,19402974147,34523231688] |