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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 1 |
| 9 | 9 |
| 10 | 45 |
| 11 | 165 |
| 12 | 495 |
| 13 | 1287 |
| 14 | 3003 |
| 15 | 6435 |
| 16 | 19305 |
| 17 | 243100 |
| 18 | 3981978 |
| 19 | 49959702 |
| 20 | 498967170 |
| 21 | 4190469570 |
| 22 | 30728937690 |
| 23 | 201931408074 |
| 24 | 1213163827326 |
| 25 | 6849350570700 |
| 26 | 39615797628550 |
| 27 | 296414654550300 |
| 28 | 3418235092302030 |
[1,0,0,0,0,0,0,0,1,9,45,165,495,1287,3003,6435, 19305,243100,3981978,49959702,498967170, 4190469570,30728937690,201931408074,1213163827326, 6849350570700,39615797628550,296414654550300, 3418235092302030] |