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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 19 |
| 7 | 58 |
| 8 | 195 |
| 9 | 651 |
| 10 | 2294 |
| 11 | 8122 |
| 12 | 29607 |
| 13 | 108276 |
| 14 | 401389 |
| 15 | 1494268 |
| 16 | 5600204 |
| 17 | 21065520 |
| 18 | 79567572 |
| 19 | 301448098 |
| 20 | 1145448216 |
| 21 | 4363328350 |
| 22 | 16659757647 |
| 23 | 63740548126 |
| 24 | 244337865925 |
| 25 | 938252884294 |
| 26 | 3608661283038 |
| 27 | 13900010654999 |
| 28 | 53614312021527 |
| 29 | 207062098878276 |
[0,0,1,2,6,19,58,195,651,2294,8122,29607,108276, 401389,1494268,5600204,21065520,79567572, 301448098,1145448216,4363328350,16659757647, 63740548126,244337865925,938252884294, 3608661283038,13900010654999,53614312021527, 207062098878276] |