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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 9 |
| 7 | 22 |
| 8 | 56 |
| 9 | 146 |
| 10 | 388 |
| 11 | 1048 |
| 12 | 2869 |
| 13 | 7942 |
| 14 | 22192 |
| 15 | 62510 |
| 16 | 177308 |
| 17 | 506008 |
| 18 | 1451866 |
| 19 | 4185788 |
| 20 | 12119696 |
| 21 | 35227748 |
| 22 | 102753800 |
| 23 | 300672368 |
| 24 | 882373261 |
| 25 | 2596389190 |
| 26 | 7658677856 |
| 27 | 22642421206 |
| 28 | 67081765932 |
| 29 | 199128719896 |
| 30 | 592179010350 |
| 31 | 1764044315540 |
[2,0,1,2,4,9,22,56,146,388,1048,2869,7942,22192, 62510,177308,506008,1451866,4185788,12119696, 35227748,102753800,300672368,882373261,2596389190, 7658677856,22642421206,67081765932,199128719896, 592179010350,1764044315540] |