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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 6 |
| 5 | 26 |
| 6 | 45 |
| 7 | 204 |
| 8 | 380 |
| 9 | 1771 |
| 10 | 3450 |
| 11 | 16380 |
| 12 | 32886 |
| 13 | 158224 |
| 14 | 324632 |
| 15 | 1577532 |
| 16 | 3290040 |
| 17 | 16112057 |
| 18 | 34034715 |
| 19 | 167710664 |
| 20 | 357919100 |
| 21 | 1772645420 |
| 22 | 3815041230 |
| 23 | 18974357220 |
| 24 | 41124015036 |
| 25 | 205263418941 |
| 26 | 447534498320 |
| 27 | 2240623268512 |
| 28 | 4910258796240 |
| 29 | 24648785802336 |
| 30 | 54257308779600 |
[1,1,4,6,26,45,204,380,1771,3450,16380,32886, 158224,324632,1577532,3290040,16112057,34034715, 167710664,357919100,1772645420,3815041230, 18974357220,41124015036,205263418941,447534498320, 2240623268512,4910258796240,24648785802336, 54257308779600] |