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) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 54 |
| 5 | 445 |
| 6 | 4821 |
| 7 | 65685 |
| 8 | 1077871 |
| 9 | 20700806 |
| 10 | 455052511 |
| 11 | 11262113374 |
| 12 | 309787170203 |
| 13 | 9373678643933 |
| 14 | 309378125685426 |
| 15 | 11059576578724264 |
| 16 | 425656284035217743 |
| 17 | 17547676024364306476 |
| 18 | 771403526860478324343 |
| 19 | 36020106660104388871845 |