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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 6 |
| 7 | 16 |
| 8 | 45 |
| 9 | 126 |
| 10 | 358 |
| 11 | 1024 |
| 12 | 2954 |
| 13 | 8580 |
| 14 | 25084 |
| 15 | 73760 |
| 16 | 218045 |
| 17 | 647670 |
| 18 | 1932230 |
| 19 | 5787520 |
| 20 | 17398270 |
| 21 | 52476700 |
| 22 | 158765300 |
| 23 | 481690080 |
| 24 | 1465239250 |
| 25 | 4467799212 |
| 26 | 13653601116 |
| 27 | 41812009216 |
| 28 | 128290240180 |
| 29 | 394338641416 |
| 30 | 1214165174712 |
[1,1,0,1,2,6,16,45,126,358,1024,2954,8580,25084, 73760,218045,647670,1932230,5787520,17398270, 52476700,158765300,481690080,1465239250, 4467799212,13653601116,41812009216,128290240180, 394338641416,1214165174712] |