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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 9 |
| 6 | 27 |
| 7 | 79 |
| 8 | 233 |
| 9 | 679 |
| 10 | 1987 |
| 11 | 5784 |
| 12 | 16864 |
| 13 | 49063 |
| 14 | 142821 |
| 15 | 415439 |
| 16 | 1208761 |
| 17 | 3516475 |
| 18 | 10232428 |
| 19 | 29778138 |
| 20 | 86682119 |
| 21 | 252382445 |
| 22 | 735040515 |
| 23 | 2141319946 |
| 24 | 6239913801 |
| 25 | 18188637903 |
| 26 | 53033228465 |
| 27 | 154674931182 |
| 28 | 451247206423 |
[0,0,1,3,9,27,79,233,679,1987,5784,16864,49063, 142821,415439,1208761,3516475,10232428,29778138, 86682119,252382445,735040515,2141319946, 6239913801,18188637903,53033228465,154674931182, 451247206423] |