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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 24 |
| 3 | 84 |
| 4 | 276 |
| 5 | 876 |
| 6 | 2724 |
| 7 | 8364 |
| 8 | 25476 |
| 9 | 77196 |
| 10 | 233124 |
| 11 | 702444 |
| 12 | 2113476 |
| 13 | 6352716 |
| 14 | 19082724 |
| 15 | 57297324 |
| 16 | 171990276 |
| 17 | 516167436 |
| 18 | 1548895524 |
| 19 | 4647473004 |
| 20 | 13943991876 |
| 21 | 41835121356 |
| 22 | 125511655524 |
| 23 | 376547549484 |
| 24 | 1129667814276 |
| 25 | 3389053774476 |
| 26 | 10167261986724 |
| 27 | 30501987286764 |
[1,6,24,84,276,876,2724,8364,25476,77196,233124, 702444,2113476,6352716,19082724,57297324, 171990276,516167436,1548895524,4647473004, 13943991876,41835121356,125511655524,376547549484, 1129667814276,3389053774476,10167261986724, 30501987286764] |