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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 16 |
| 6 | 49 |
| 7 | 156 |
| 8 | 511 |
| 9 | 1723 |
| 10 | 5942 |
| 11 | 20817 |
| 12 | 73938 |
| 13 | 265611 |
| 14 | 963225 |
| 15 | 3521667 |
| 16 | 12966696 |
| 17 | 48037862 |
| 18 | 178936340 |
| 19 | 669748197 |
| 20 | 2517688316 |
| 21 | 9501290664 |
| 22 | 35982633397 |
| 23 | 136708135198 |
| 24 | 520914346328 |
| 25 | 1990230295787 |
| 26 | 7622765394301 |
| 27 | 29262526895379 |
| 28 | 112571409093256 |
[0,1,1,2,6,16,49,156,511,1723,5942,20817,73938, 265611,963225,3521667,12966696,48037862,178936340, 669748197,2517688316,9501290664,35982633397, 136708135198,520914346328,1990230295787, 7622765394301,29262526895379,112571409093256] |