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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 0 |
| 5 | 10 |
| 6 | 36 |
| 7 | 35 |
| 8 | 448 |
| 9 | 450 |
| 10 | 4600 |
| 11 | 13167 |
| 12 | 45408 |
| 13 | 240006 |
| 14 | 670124 |
| 15 | 3863835 |
| 16 | 13209088 |
| 17 | 60533974 |
| 18 | 268324056 |
| 19 | 1089776654 |
| 20 | 5328589520 |
| 21 | 22065836226 |
| 22 | 106289169448 |
| 23 | 481033496803 |
| 24 | 2231768294208 |
| 25 | 10748702587800 |
| 26 | 49858509230920 |
| 27 | 245664498591891 |
| 28 | 1175943617623264 |
[1,1,0,3,0,10,36,35,448,450,4600,13167,45408, 240006,670124,3863835,13209088,60533974,268324056, 1089776654,5328589520,22065836226,106289169448, 481033496803,2231768294208,10748702587800, 49858509230920,245664498591891,1175943617623264] |