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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 3 |
| 5 | 3 |
| 6 | 33 |
| 7 | 72 |
| 8 | 120 |
| 9 | 583 |
| 10 | 1731 |
| 11 | 3888 |
| 12 | 13759 |
| 13 | 44775 |
| 14 | 119793 |
| 15 | 381220 |
| 16 | 1250328 |
| 17 | 3682284 |
| 18 | 11455153 |
| 19 | 37174428 |
| 20 | 114947724 |
| 21 | 359381467 |
| 22 | 1157319135 |
| 23 | 3663615552 |
| 24 | 11581104121 |
| 25 | 37220909916 |
| 26 | 119192219799 |
| 27 | 380580143110 |
| 28 | 1225279436706 |
| 29 | 3948906772872 |
| 30 | 12705801908002 |
[1,0,0,3,3,3,33,72,120,583,1731,3888,13759,44775, 119793,381220,1250328,3682284,11455153,37174428, 114947724,359381467,1157319135,3663615552, 11581104121,37220909916,119192219799,380580143110, 1225279436706,3948906772872,12705801908002] |