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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 53 |
| 5 | 177 |
| 6 | 828 |
| 7 | 3092 |
| 8 | 14784 |
| 9 | 57789 |
| 10 | 280272 |
| 11 | 1135447 |
| 12 | 5552568 |
| 13 | 23024141 |
| 14 | 113220356 |
| 15 | 477899480 |
| 16 | 2359089266 |
| 17 | 10094151186 |
| 18 | 49965552101 |
| 19 | 216128476308 |
| 20 | 1071992173208 |
| 21 | 4678195921440 |
| 22 | 23239176677578 |
| 23 | 102166556126257 |
| 24 | 508113249104213 |
| 25 | 2247796432093211 |
| 26 | 11189390004754332 |
| 27 | 49765229004840975 |
[1,1,4,12,53,177,828,3092,14784,57789,280272, 1135447,5552568,23024141,113220356,477899480, 2359089266,10094151186,49965552101,216128476308, 1071992173208,4678195921440,23239176677578, 102166556126257,508113249104213,2247796432093211, 11189390004754332,49765229004840975] |