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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 6 |
| 5 | 14 |
| 6 | 40 |
| 7 | 56 |
| 8 | 100 |
| 9 | 332 |
| 10 | 1200 |
| 11 | 1696 |
| 12 | 7000 |
| 13 | 30514 |
| 14 | 146344 |
| 15 | 327236 |
| 16 | 566792 |
| 17 | 3052270 |
| 18 | 16994324 |
| 19 | 24033604 |
| 20 | 146190716 |
| 21 | 936077324 |
| 22 | 6138269514 |
| 23 | 42081855636 |
| 24 | 111338124722 |
| 25 | 810553782854 |
| 26 | 6225981742592 |
| 27 | 48626471887292 |
| 28 | 68768216033362 |
| 29 | 562892107725410 |
| 30 | 4743013205833238 |
[0,2,4,6,14,40,56,100,332,1200,1696,7000,30514, 146344,327236,566792,3052270,16994324,24033604, 146190716,936077324,6138269514,42081855636, 111338124722,810553782854,6225981742592, 48626471887292,68768216033362,562892107725410, 4743013205833238] |