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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 0 |
| 4 | 6 |
| 5 | 0 |
| 6 | 20 |
| 7 | 0 |
| 8 | 70 |
| 9 | 2 |
| 10 | 252 |
| 11 | 22 |
| 12 | 924 |
| 13 | 156 |
| 14 | 3432 |
| 15 | 910 |
| 16 | 12870 |
| 17 | 4760 |
| 18 | 48622 |
| 19 | 23256 |
| 20 | 184796 |
| 21 | 108528 |
| 22 | 705894 |
| 23 | 490314 |
| 24 | 2708204 |
| 25 | 2163150 |
| 26 | 10430500 |
| 27 | 9373652 |
| 28 | 40313160 |
| 29 | 40060078 |
| 30 | 156305070 |
| 31 | 169345560 |
| 32 | 607812102 |
| 33 | 709645552 |
| 34 | 2369918628 |
| 35 | 2952780320 |
[1,0,2,0,6,0,20,0,70,2,252,22,924,156,3432,910, 12870,4760,48622,23256,184796,108528,705894, 490314,2708204,2163150,10430500,9373652,40313160, 40060078,156305070,169345560,607812102,709645552, 2369918628,2952780320] |