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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 4 |
| 5 | 16 |
| 6 | 38 |
| 7 | 132 |
| 8 | 342 |
| 9 | 1144 |
| 10 | 3134 |
| 11 | 10370 |
| 12 | 29526 |
| 13 | 97458 |
| 14 | 285458 |
| 15 | 942920 |
| 16 | 2822310 |
| 17 | 9341008 |
| 18 | 28440970 |
| 19 | 94358558 |
| 20 | 291294678 |
| 21 | 968853072 |
| 22 | 3025232480 |
| 23 | 10086634316 |
| 24 | 31797822936 |
| 25 | 106265437078 |
| 26 | 337731551446 |
| 27 | 1131117792978 |
| 28 | 3620119437762 |
| 29 | 12148796744234 |
| 30 | 39118879440938 |
[0,0,2,4,16,38,132,342,1144,3134,10370,29526, 97458,285458,942920,2822310,9341008,28440970, 94358558,291294678,968853072,3025232480, 10086634316,31797822936,106265437078,337731551446, 1131117792978,3620119437762,12148796744234, 39118879440938] |