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) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 20 |
| 4 | 133 |
| 5 | 1047 |
| 6 | 9754 |
| 7 | 103203 |
| 8 | 1229330 |
| 9 | 16198452 |
| 10 | 234110702 |
| 11 | 3675679471 |
| 12 | 62287376870 |
| 13 | 1132138152251 |
| 14 | 21963847972941 |
| 15 | 452786198062541 |
| 16 | 9881445268293457 |
| 17 | 227522503290656371 |
| 18 | 5510876754647261442 |
| 19 | 140040543831299600637 |
| 20 | 3724688873146823853387 |