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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 27 |
| 6 | 110 |
| 7 | 460 |
| 8 | 1948 |
| 9 | 8296 |
| 10 | 35400 |
| 11 | 151056 |
| 12 | 643892 |
| 13 | 2740216 |
| 14 | 11639416 |
| 15 | 49340080 |
| 16 | 208727176 |
| 17 | 881212272 |
| 18 | 3713043152 |
| 19 | 15615663008 |
| 20 | 65555425780 |
| 21 | 274734294328 |
| 22 | 1149506252376 |
| 23 | 4802212126704 |
| 24 | 20032666552664 |
| 25 | 83452195924304 |
| 26 | 347192769717040 |
| 27 | 1442672957396320 |
[1,2,7,27,110,460,1948,8296,35400,151056,643892, 2740216,11639416,49340080,208727176,881212272, 3713043152,15615663008,65555425780,274734294328, 1149506252376,4802212126704,20032666552664, 83452195924304,347192769717040,1442672957396320] |