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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 18 |
| 3 | 45 |
| 4 | 116 |
| 5 | 293 |
| 6 | 735 |
| 7 | 1844 |
| 8 | 4626 |
| 9 | 11611 |
| 10 | 29151 |
| 11 | 73200 |
| 12 | 183828 |
| 13 | 461671 |
| 14 | 1159483 |
| 15 | 2912066 |
| 16 | 7313756 |
| 17 | 18368803 |
| 18 | 46134069 |
| 19 | 115867838 |
| 20 | 291007480 |
| 21 | 730878941 |
| 22 | 1835636845 |
| 23 | 4610288394 |
| 24 | 11578956554 |
| 25 | 29081095145 |
| 26 | 73038541289 |
| 27 | 183439739500 |
[4,18,45,116,293,735,1844,4626,11611,29151,73200, 183828,461671,1159483,2912066,7313756,18368803, 46134069,115867838,291007480,730878941,1835636845, 4610288394,11578956554,29081095145,73038541289, 183439739500] |