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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 46 |
| 6 | 140 |
| 7 | 464 |
| 8 | 1580 |
| 9 | 5538 |
| 10 | 19804 |
| 11 | 71884 |
| 12 | 264204 |
| 13 | 980778 |
| 14 | 3671652 |
| 15 | 13843808 |
| 16 | 52519836 |
| 17 | 200320878 |
| 18 | 767688176 |
| 19 | 2954410484 |
| 20 | 11412815256 |
| 21 | 44237340702 |
| 22 | 171997272012 |
| 23 | 670612394118 |
| 24 | 2621415708492 |
| 25 | 10271274034254 |
[2,6,16,46,140,464,1580,5538,19804,71884,264204, 980778,3671652,13843808,52519836,200320878, 767688176,2954410484,11412815256,44237340702, 171997272012,670612394118,2621415708492, 10271274034254] |