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 | 1 |
| 3 | 8 |
| 4 | 66 |
| 5 | 512 |
| 6 | 5269 |
| 7 | 57459 |
| 8 | 711742 |
| 9 | 9610222 |
| 10 | 139735699 |
| 11 | 2183555015 |
| 12 | 36543300668 |
| 13 | 649320343729 |
| 14 | 12174674648730 |
| 15 | 240360451018461 |
| 16 | 4975239937954534 |
| 17 | 107600744797471150 |
| 18 | 2426579187889852885 |
| 19 | 56901290353169050995 |
| 20 | 1384258146777832889697 |