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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 28 |
| 5 | 80 |
| 6 | 240 |
| 7 | 756 |
| 8 | 2424 |
| 9 | 7904 |
| 10 | 26368 |
| 11 | 89324 |
| 12 | 305480 |
| 13 | 1056480 |
| 14 | 3693280 |
| 15 | 13011712 |
| 16 | 46144768 |
| 17 | 164775296 |
| 18 | 592005184 |
| 19 | 2137741872 |
| 20 | 7754971680 |
| 21 | 28258590336 |
| 22 | 103392253824 |
| 23 | 379649300944 |
| 24 | 1398639670240 |
| 25 | 5168935430656 |
| 26 | 19158863140288 |
| 27 | 71201979973480 |
| 28 | 265265435150064 |
| 29 | 990589140446528 |
| 30 | 3707399290547776 |
[1,2,4,10,28,80,240,756,2424,7904,26368,89324, 305480,1056480,3693280,13011712,46144768, 164775296,592005184,2137741872,7754971680, 28258590336,103392253824,379649300944, 1398639670240,5168935430656,19158863140288, 71201979973480,265265435150064,990589140446528, 3707399290547776] |