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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 34 |
| 3 | 210 |
| 4 | 830 |
| 5 | 2520 |
| 6 | 6412 |
| 7 | 14364 |
| 8 | 29220 |
| 9 | 55110 |
| 10 | 97790 |
| 11 | 165022 |
| 12 | 266994 |
| 13 | 416780 |
| 14 | 630840 |
| 15 | 929560 |
| 16 | 1337832 |
| 17 | 1885674 |
| 18 | 2608890 |
| 19 | 3549770 |
| 20 | 4757830 |
| 21 | 6290592 |
| 22 | 8214404 |
| 23 | 10605300 |
| 24 | 13549900 |
| 25 | 17146350 |
| 26 | 21505302 |
| 27 | 26750934 |
| 28 | 33022010 |
[0,2,34,210,830,2520,6412,14364,29220,55110,97790, 165022,266994,416780,630840,929560,1337832, 1885674,2608890,3549770,4757830,6290592,8214404, 10605300,13549900,17146350,21505302,26750934, 33022010] |