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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 15 |
| 4 | 64 |
| 5 | 220 |
| 6 | 672 |
| 7 | 1904 |
| 8 | 5120 |
| 9 | 13248 |
| 10 | 33280 |
| 11 | 81664 |
| 12 | 196608 |
| 13 | 465920 |
| 14 | 1089536 |
| 15 | 2519040 |
| 16 | 5767168 |
| 17 | 13090816 |
| 18 | 29491200 |
| 19 | 65994752 |
| 20 | 146800640 |
| 21 | 324796416 |
| 22 | 715128832 |
| 23 | 1567621120 |
| 24 | 3422552064 |
| 25 | 7444889600 |
| 26 | 16139681792 |
| 27 | 34879832064 |
| 28 | 75161927680 |
| 29 | 161531035648 |
| 30 | 346281738240 |
[0,2,15,64,220,672,1904,5120,13248,33280,81664, 196608,465920,1089536,2519040,5767168,13090816, 29491200,65994752,146800640,324796416,715128832, 1567621120,3422552064,7444889600,16139681792, 34879832064,75161927680,161531035648,346281738240] |