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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 73 |
| 5 | 271 |
| 6 | 1080 |
| 7 | 4279 |
| 8 | 17742 |
| 9 | 73334 |
| 10 | 311463 |
| 11 | 1320901 |
| 12 | 5714076 |
| 13 | 24652208 |
| 14 | 108136214 |
| 15 | 472772076 |
| 16 | 2095411822 |
| 17 | 9259635607 |
| 18 | 41376583416 |
| 19 | 184401748204 |
| 20 | 829589409023 |
| 21 | 3722631449396 |
| 22 | 16842693737703 |
| 23 | 76013872054272 |
| 24 | 345562604149092 |
| 25 | 1567259945508055 |
| 26 | 7153952350547666 |
| 27 | 32583203020133357 |
[1,2,6,20,73,271,1080,4279,17742,73334,311463, 1320901,5714076,24652208,108136214,472772076, 2095411822,9259635607,41376583416,184401748204, 829589409023,3722631449396,16842693737703, 76013872054272,345562604149092,1567259945508055, 7153952350547666,32583203020133357] |