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 | 3 |
| 4 | 7 |
| 5 | 23 |
| 6 | 83 |
| 7 | 405 |
| 8 | 2113 |
| 9 | 12657 |
| 10 | 82297 |
| 11 | 596483 |
| 12 | 4698655 |
| 13 | 40071743 |
| 14 | 367854835 |
| 15 | 3622508685 |
| 16 | 38027715185 |
| 17 | 424060091065 |
| 18 | 5006620130753 |
| 19 | 62395131973755 |
| 20 | 818456924866815 |
| 21 | 11271715349614463 |