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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 10 |
| 7 | 31 |
| 8 | 134 |
| 9 | 439 |
| 10 | 1604 |
| 11 | 5088 |
| 12 | 17115 |
| 13 | 54199 |
| 14 | 176073 |
| 15 | 552856 |
| 16 | 1755516 |
| 17 | 5472509 |
| 18 | 17149688 |
| 19 | 53191180 |
| 20 | 165306987 |
| 21 | 510614655 |
| 22 | 1578127066 |
| 23 | 4859554763 |
| 24 | 14963066678 |
| 25 | 45966984378 |
| 26 | 141165413462 |
| 27 | 432876102395 |
| 28 | 1326862831744 |
[0,0,0,1,2,10,31,134,439,1604,5088,17115,54199, 176073,552856,1755516,5472509,17149688,53191180, 165306987,510614655,1578127066,4859554763, 14963066678,45966984378,141165413462,432876102395, 1326862831744] |