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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 18 |
| 6 | 42 |
| 7 | 90 |
| 8 | 228 |
| 9 | 498 |
| 10 | 1152 |
| 11 | 2274 |
| 12 | 5460 |
| 13 | 10308 |
| 14 | 20868 |
| 15 | 39222 |
| 16 | 78126 |
| 17 | 151092 |
| 18 | 306144 |
| 19 | 596796 |
| 20 | 1204734 |
| 21 | 2359518 |
| 22 | 4720854 |
| 23 | 9229200 |
| 24 | 18329442 |
| 25 | 35889966 |
| 26 | 71284524 |
| 27 | 140430234 |
| 28 | 279790956 |
| 29 | 554351988 |
| 30 | 1105988208 |
| 31 | 2195249184 |
| 32 | 4371548958 |
| 33 | 8665192968 |
[1,1,1,2,6,18,42,90,228,498,1152,2274,5460,10308, 20868,39222,78126,151092,306144,596796,1204734, 2359518,4720854,9229200,18329442,35889966, 71284524,140430234,279790956,554351988,1105988208, 2195249184,4371548958,8665192968] |