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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 100 |
| 5 | 332 |
| 6 | 994 |
| 7 | 2774 |
| 8 | 7368 |
| 9 | 18872 |
| 10 | 47014 |
| 11 | 114578 |
| 12 | 274300 |
| 13 | 647012 |
| 14 | 1507146 |
| 15 | 3473198 |
| 16 | 7929616 |
| 17 | 17956592 |
| 18 | 40369870 |
| 19 | 90177194 |
| 20 | 200277636 |
| 21 | 442498652 |
| 22 | 973078066 |
| 23 | 2130705926 |
| 24 | 4647288280 |
| 25 | 10099883432 |
| 26 | 21877489014 |
| 27 | 47244639554 |
| 28 | 101737037068 |
[2,6,26,100,332,994,2774,7368,18872,47014,114578, 274300,647012,1507146,3473198,7929616,17956592, 40369870,90177194,200277636,442498652,973078066, 2130705926,4647288280,10099883432,21877489014, 47244639554,101737037068] |