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 | 47293 |
| 8 | 545835 |
| 9 | 7087261 |
| 10 | 102247563 |
| 11 | 1622632572 |
| 12 | 28091567570 |
| 13 | 526858347730 |
| 14 | 10641342953670 |
| 15 | 230283190536542 |
| 16 | 5315654669985946 |
| 17 | 130370766690581274 |
| 18 | 3385534653313192094 |
| 19 | 92801587015186096762 |
| 20 | 2677687786557636155446 |