The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 17 |
| 3 | 80 |
| 4 | 323 |
| 5 | 1214 |
| 6 | 4373 |
| 7 | 15308 |
| 8 | 52487 |
| 9 | 177146 |
| 10 | 590489 |
| 11 | 1948616 |
| 12 | 6377291 |
| 13 | 20726198 |
| 14 | 66961565 |
| 15 | 215233604 |
| 16 | 688747535 |
| 17 | 2195382770 |
| 18 | 6973568801 |
| 19 | 22082967872 |
| 20 | 69735688019 |
| 21 | 219667417262 |
| 22 | 690383311397 |
| 23 | 2165293113020 |
| 24 | 6778308875543 |
| 25 | 21182215236074 |
| 26 | 66088511536553 |
| 27 | 205891132094648 |
[2,17,80,323,1214,4373,15308,52487,177146,590489, 1948616,6377291,20726198,66961565,215233604, 688747535,2195382770,6973568801,22082967872, 69735688019,219667417262,690383311397, 2165293113020,6778308875543,21182215236074, 66088511536553,205891132094648] |