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 | 13 |
| 4 | 75 |
| 5 | 541 |
| 6 | 4683 |
| 7 | 47292 |
| 8 | 545818 |
| 9 | 7086954 |
| 10 | 102241902 |
| 11 | 1622523210 |
| 12 | 28089336198 |
| 13 | 526810157874 |
| 14 | 10640241569958 |
| 15 | 230256584914356 |
| 16 | 5314976561846952 |
| 17 | 130352566702702344 |
| 18 | 3385021286975255928 |
| 19 | 92786398312428612792 |
| 20 | 2677217312112863784264 |