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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 72 |
| 7 | 272 |
| 8 | 1064 |
| 9 | 4271 |
| 10 | 17497 |
| 11 | 72843 |
| 12 | 307307 |
| 13 | 1310792 |
| 14 | 5643555 |
| 15 | 24493270 |
| 16 | 107043258 |
| 17 | 470668034 |
| 18 | 2080681402 |
| 19 | 9242180923 |
| 20 | 41229189089 |
| 21 | 184634145428 |
| 22 | 829732117279 |
| 23 | 3740636883361 |
| 24 | 16912812764736 |
| 25 | 76673344515050 |
| 26 | 348449086540653 |
| 27 | 1587154540744158 |