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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 15 |
| 6 | 47 |
| 7 | 127 |
| 8 | 363 |
| 9 | 978 |
| 10 | 2778 |
| 11 | 7624 |
| 12 | 21566 |
| 13 | 60584 |
| 14 | 172221 |
| 15 | 488978 |
| 16 | 1398457 |
| 17 | 4001323 |
| 18 | 11490717 |
| 19 | 33037548 |
| 20 | 95195793 |
| 21 | 274609124 |
| 22 | 793298293 |
| 23 | 2294114542 |
| 24 | 6641070332 |
| 25 | 19241453969 |
| 26 | 55795142707 |
| 27 | 161910611244 |
[0,0,1,5,15,47,127,363,978,2778,7624,21566,60584, 172221,488978,1398457,4001323,11490717,33037548, 95195793,274609124,793298293,2294114542, 6641070332,19241453969,55795142707,161910611244] |