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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 5 |
| 6 | 20 |
| 7 | 47 |
| 8 | 126 |
| 9 | 327 |
| 10 | 1041 |
| 11 | 2854 |
| 12 | 8083 |
| 13 | 24892 |
| 14 | 76208 |
| 15 | 222509 |
| 16 | 686079 |
| 17 | 2174516 |
| 18 | 6673802 |
| 19 | 20646366 |
| 20 | 66232829 |
| 21 | 210542762 |
| 22 | 662048460 |
| 23 | 2129820354 |
| 24 | 6910328426 |
| 25 | 22163635347 |
| 26 | 71624432296 |
| 27 | 234661293959 |
| 28 | 765583825870 |
| 29 | 2494320434589 |
| 30 | 8213432381547 |
| 31 | 27116116390705 |
| 32 | 89225059889125 |
| 33 | 295111869092137 |
[1,0,1,1,4,5,20,47,126,327,1041,2854,8083,24892, 76208,222509,686079,2174516,6673802,20646366, 66232829,210542762,662048460,2129820354, 6910328426,22163635347,71624432296,234661293959, 765583825870,2494320434589,8213432381547, 27116116390705,89225059889125,295111869092137] |