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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 66 |
| 5 | 247 |
| 6 | 966 |
| 7 | 3907 |
| 8 | 16161 |
| 9 | 68187 |
| 10 | 292988 |
| 11 | 1277679 |
| 12 | 5638228 |
| 13 | 25121213 |
| 14 | 112897471 |
| 15 | 511377308 |
| 16 | 2332359467 |
| 17 | 10700837502 |
| 18 | 49349356380 |
| 19 | 228656721764 |
| 20 | 1064040168553 |
| 21 | 4970759755902 |
| 22 | 23302285912883 |
| 23 | 109582451702144 |
| 24 | 516824544225503 |
| 25 | 2444056861503320 |
| 26 | 11586473757680157 |
| 27 | 55052037361026731 |
[1,2,6,19,66,247,966,3907,16161,68187,292988, 1277679,5638228,25121213,112897471,511377308, 2332359467,10700837502,49349356380,228656721764, 1064040168553,4970759755902,23302285912883, 109582451702144,516824544225503,2444056861503320, 11586473757680157,55052037361026731] |