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 | 2 |
| 2 | 5 |
| 3 | 18 |
| 4 | 69 |
| 5 | 306 |
| 6 | 1497 |
| 7 | 7890 |
| 8 | 45033 |
| 9 | 273474 |
| 10 | 1760301 |
| 11 | 11961522 |
| 12 | 85265325 |
| 13 | 636026418 |
| 14 | 4947725889 |
| 15 | 40019230386 |
| 16 | 335868650577 |
| 17 | 2918173355010 |
| 18 | 26199114476373 |
| 19 | 242657102748114 |
| 20 | 2314964975130261 |
| 21 | 22717352863875762 |
| 22 | 229029972003647145 |
| 23 | 2369438933865972498 |