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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 75 |
| 5 | 294 |
| 6 | 1201 |
| 7 | 5078 |
| 8 | 21848 |
| 9 | 95576 |
| 10 | 424532 |
| 11 | 1906655 |
| 12 | 8636683 |
| 13 | 39450664 |
| 14 | 181496328 |
| 15 | 839654187 |
| 16 | 3904476015 |
| 17 | 18243215608 |
| 18 | 85580996797 |
| 19 | 402880951625 |
| 20 | 1902911971526 |
| 21 | 9014705935470 |
| 22 | 42816705935196 |
| 23 | 203856822736059 |
| 24 | 972780079340487 |
| 25 | 4651358785357559 |
| 26 | 22281663912308269 |
| 27 | 106922886723397286 |
[1,2,6,20,75,294,1201,5078,21848,95576,424532, 1906655,8636683,39450664,181496328,839654187, 3904476015,18243215608,85580996797,402880951625, 1902911971526,9014705935470,42816705935196, 203856822736059,972780079340487,4651358785357559, 22281663912308269,106922886723397286] |