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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 30 |
| 2 | 144 |
| 3 | 700 |
| 4 | 3418 |
| 5 | 16736 |
| 6 | 82098 |
| 7 | 403274 |
| 8 | 1982980 |
| 9 | 9758780 |
| 10 | 48058110 |
| 11 | 236801010 |
| 12 | 1167371680 |
| 13 | 5757241450 |
| 14 | 28403776808 |
| 15 | 140176438936 |
| 16 | 691982963722 |
| 17 | 3416834220692 |
| 18 | 16875210619810 |
| 19 | 83360735329998 |
| 20 | 411862694955416 |
[1,30,144,700,3418,16736,82098,403274,1982980, 9758780,48058110,236801010,1167371680,5757241450, 28403776808,140176438936,691982963722, 3416834220692,16875210619810,83360735329998, 411862694955416] |