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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 24 |
| 7 | 64 |
| 8 | 167 |
| 9 | 460 |
| 10 | 1256 |
| 11 | 3532 |
| 12 | 9910 |
| 13 | 28280 |
| 14 | 80756 |
| 15 | 232984 |
| 16 | 673371 |
| 17 | 1958982 |
| 18 | 5710900 |
| 19 | 16722156 |
| 20 | 49061276 |
| 21 | 144387320 |
| 22 | 425674212 |
| 23 | 1257774336 |
| 24 | 3721938064 |
| 25 | 11032243612 |
| 26 | 32740524236 |
| 27 | 97287632048 |
| 28 | 289369653892 |
[1,1,2,4,10,24,64,167,460,1256,3532,9910,28280, 80756,232984,673371,1958982,5710900,16722156, 49061276,144387320,425674212,1257774336, 3721938064,11032243612,32740524236,97287632048, 289369653892] |