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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 55 |
| 5 | 190 |
| 6 | 902 |
| 7 | 3398 |
| 8 | 16472 |
| 9 | 65382 |
| 10 | 320484 |
| 11 | 1312459 |
| 12 | 6474503 |
| 13 | 27104304 |
| 14 | 134256960 |
| 15 | 571321161 |
| 16 | 2837484435 |
| 17 | 12227247005 |
| 18 | 60836420112 |
| 19 | 264787231957 |
| 20 | 1319103859564 |
| 21 | 5788272875402 |
| 22 | 28861599810455 |
| 23 | 127506273555132 |
| 24 | 636189290776676 |
| 25 | 2826744133116800 |
| 26 | 14110771051321589 |
| 27 | 63006692533646008 |
[1,1,4,12,55,190,902,3398,16472,65382,320484, 1312459,6474503,27104304,134256960,571321161, 2837484435,12227247005,60836420112,264787231957, 1319103859564,5788272875402,28861599810455, 127506273555132,636189290776676,2826744133116800, 14110771051321589,63006692533646008] |