This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 2 | 5 |
| 3 | 15 |
| 4 | 50 |
| 5 | 150 |
| 6 | 455 |
| 7 | 1365 |
| 8 | 4100 |
| 9 | 12300 |
| 10 | 36905 |
| 11 | 110715 |
| 12 | 332150 |
| 13 | 996450 |
| 14 | 2989355 |
| 15 | 8968065 |
| 16 | 26904200 |
| 17 | 80712600 |
| 18 | 242137805 |
| 19 | 726413415 |
| 20 | 2179240250 |
| 21 | 6537720750 |
| 22 | 19613162255 |
| 23 | 58839486765 |
| 24 | 176518460300 |
| 25 | 529555380900 |
| 26 | 1588666142705 |
| 27 | 4765998428115 |
| 28 | 14297995284350 |