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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 50 |
| 5 | 138 |
| 6 | 374 |
| 7 | 994 |
| 8 | 2610 |
| 9 | 6778 |
| 10 | 17414 |
| 11 | 44346 |
| 12 | 112034 |
| 13 | 280970 |
| 14 | 700038 |
| 15 | 1733706 |
| 16 | 4269970 |
| 17 | 10463154 |
| 18 | 25518198 |
| 19 | 61962458 |
| 20 | 149839602 |
| 21 | 360958306 |
| 22 | 866405702 |
| 23 | 2072579058 |
| 24 | 4942074082 |
| 25 | 11748730482 |
| 26 | 27849974598 |
| 27 | 65837539522 |
| 28 | 155236876018 |
| 29 | 365125130490 |
| 30 | 856767548022 |
[1,2,6,18,50,138,374,994,2610,6778,17414,44346, 112034,280970,700038,1733706,4269970,10463154, 25518198,61962458,149839602,360958306,866405702, 2072579058,4942074082,11748730482,27849974598, 65837539522,155236876018,365125130490, 856767548022] |