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 | 4 |
| 3 | 28 |
| 4 | 215 |
| 5 | 1983 |
| 6 | 19789 |
| 7 | 213698 |
| 8 | 2426851 |
| 9 | 28661509 |
| 10 | 348287354 |
| 11 | 4322627557 |
| 12 | 54508747790 |
| 13 | 695534616050 |
| 14 | 8953637420349 |
| 15 | 116002300640637 |
| 16 | 1509724588732027 |
| 17 | 19707310304585212 |
| 18 | 257698683361191598 |
| 19 | 3372154116182404890 |
| 20 | 44121356408759264549 |