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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 28 |
| 4 | 120 |
| 5 | 538 |
| 6 | 2493 |
| 7 | 11854 |
| 8 | 57558 |
| 9 | 284392 |
| 10 | 1426038 |
| 11 | 7241356 |
| 12 | 37173304 |
| 13 | 192638992 |
| 14 | 1006564439 |
| 15 | 5297715628 |
| 16 | 28061959428 |
| 17 | 149491856978 |
| 18 | 800425486692 |
| 19 | 4305263668514 |
| 20 | 23251846197766 |
| 21 | 126044501870378 |
| 22 | 685569373724964 |
| 23 | 3740339567665558 |
| 24 | 20463965229643218 |
| 25 | 112250484320225118 |
[1,2,7,28,120,538,2493,11854,57558,284392,1426038, 7241356,37173304,192638992,1006564439,5297715628, 28061959428,149491856978,800425486692, 4305263668514,23251846197766,126044501870378, 685569373724964,3740339567665558, 20463965229643218,112250484320225118] |