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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 14 |
| 4 | 56 |
| 5 | 262 |
| 6 | 1348 |
| 7 | 7574 |
| 8 | 45616 |
| 9 | 292442 |
| 10 | 1978788 |
| 11 | 14060654 |
| 12 | 104403304 |
| 13 | 807162070 |
| 14 | 6476169012 |
| 15 | 53781863598 |
| 16 | 461194543136 |
| 17 | 4075567775538 |
| 18 | 37048022605956 |
| 19 | 345883045698222 |
| 20 | 3311798037556952 |
| 21 | 32480125869403430 |
[1,2,4,14,56,262,1348,7574,45616,292442,1978788, 14060654,104403304,807162070,6476169012, 53781863598,461194543136,4075567775538, 37048022605956,345883045698222,3311798037556952, 32480125869403430] |