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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 18 |
| 6 | 56 |
| 7 | 163 |
| 8 | 459 |
| 9 | 1286 |
| 10 | 3640 |
| 11 | 10479 |
| 12 | 30659 |
| 13 | 90738 |
| 14 | 270092 |
| 15 | 804833 |
| 16 | 2393929 |
| 17 | 7098790 |
| 18 | 20984188 |
| 19 | 61872587 |
| 20 | 182130495 |
| 21 | 535698422 |
| 22 | 1575478728 |
| 23 | 4635125097 |
| 24 | 13645054833 |
| 25 | 40196623234 |
| 26 | 118493318904 |
| 27 | 349506908369 |
| 28 | 1031426887149 |
[0,0,0,1,5,18,56,163,459,1286,3640,10479,30659, 90738,270092,804833,2393929,7098790,20984188, 61872587,182130495,535698422,1575478728, 4635125097,13645054833,40196623234,118493318904, 349506908369,1031426887149] |