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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 26 |
| 5 | 90 |
| 6 | 321 |
| 7 | 1137 |
| 8 | 4214 |
| 9 | 16216 |
| 10 | 62231 |
| 11 | 242631 |
| 12 | 968206 |
| 13 | 3885959 |
| 14 | 15683551 |
| 15 | 64124180 |
| 16 | 264329268 |
| 17 | 1093562973 |
| 18 | 4555281146 |
| 19 | 19109956151 |
| 20 | 80485553261 |
| 21 | 340317180230 |
| 22 | 1446312032121 |
| 23 | 6171289488079 |
| 24 | 26410646950066 |
| 25 | 113417718246251 |
| 26 | 488757470747155 |
| 27 | 2111927869755452 |
| 28 | 9148624023241031 |
[1,1,3,9,26,90,321,1137,4214,16216,62231,242631, 968206,3885959,15683551,64124180,264329268, 1093562973,4555281146,19109956151,80485553261, 340317180230,1446312032121,6171289488079, 26410646950066,113417718246251,488757470747155, 2111927869755452,9148624023241031] |