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) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 15 |
| 5 | 36 |
| 6 | 126 |
| 7 | 372 |
| 8 | 1239 |
| 9 | 3910 |
| 10 | 12848 |
| 11 | 41581 |
| 12 | 136578 |
| 13 | 447188 |
| 14 | 1473342 |
| 15 | 4855704 |
| 16 | 16053831 |
| 17 | 53138244 |
| 18 | 176233968 |
| 19 | 585202262 |
| 20 | 1945964080 |
| 21 | 6478043121 |
| 22 | 21588979877 |
| 23 | 72016891509 |
| 24 | 240452892570 |
| 25 | 803489258286 |
| 26 | 2686964354376 |
| 27 | 8991840800137 |
| 28 | 30110638705890 |