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 | 12 |
| 4 | 73 |
| 5 | 556 |
| 6 | 4737 |
| 7 | 44122 |
| 8 | 453441 |
| 9 | 5226984 |
| 10 | 69703201 |
| 11 | 1132247854 |
| 12 | 22865062497 |
| 13 | 541274154604 |
| 14 | 13810143608913 |
| 15 | 361165919643666 |
| 16 | 9534875308290433 |
| 17 | 254667431232941008 |
| 18 | 6928956222876625473 |
| 19 | 193066959857334885334 |
| 20 | 5521621116955849623201 |