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 | 15 |
| 4 | 97 |
| 5 | 785 |
| 6 | 7523 |
| 7 | 83615 |
| 8 | 1053281 |
| 9 | 14838177 |
| 10 | 230832867 |
| 11 | 3929944623 |
| 12 | 72633052545 |
| 13 | 1447981700529 |
| 14 | 30960823851267 |
| 15 | 706676217730239 |
| 16 | 17145815895371073 |
| 17 | 440594781536265537 |
| 18 | 11952178787661839427 |
| 19 | 341291300477569866831 |
| 20 | 10231558345117929439521 |