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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 18 |
| 6 | 60 |
| 7 | 191 |
| 8 | 589 |
| 9 | 1775 |
| 10 | 5257 |
| 11 | 15360 |
| 12 | 44394 |
| 13 | 127171 |
| 14 | 361595 |
| 15 | 1021693 |
| 16 | 2871245 |
| 17 | 8031246 |
| 18 | 22372344 |
| 19 | 62096135 |
| 20 | 171797257 |
| 21 | 473928875 |
| 22 | 1304007889 |
| 23 | 3579517116 |
| 24 | 9804791910 |
| 25 | 26804181643 |
| 26 | 73145473655 |
| 27 | 199276078201 |
| 28 | 542076556949 |
| 29 | 1472491141770 |
| 30 | 3994615719732 |
[0,0,0,1,5,18,60,191,589,1775,5257,15360,44394, 127171,361595,1021693,2871245,8031246,22372344, 62096135,171797257,473928875,1304007889, 3579517116,9804791910,26804181643,73145473655, 199276078201,542076556949,1472491141770, 3994615719732] |